History of Floods, Snowstorms
and Tornados in Pittsburgh

The History of Floods, Snowstorms
and Tornados in Pittsburgh

Blame It On The Ice Age?
Flood Stage - 24 Feet
100-Year/500-Year Floods
Attempts At Flood Control
Record Floods In Pittsburgh
The Calm After The Storm
Other Natural Disasters:
Let It Snow! Let It Snow!
Brrrrrrrrrr!
Sometimes It Can Get Hot, Too
Twisters And Macro-Bursts
Did Someone Say Earthquakes?
NOAA National Weather Service - Pittsburgh
Daily Climate Data (1996-present)
Pittsburgh Historical Climate Records

The City of Pittsburgh lies under a menacing
blanket of storm clouds - March 15, 2012.
The City of Pittsburgh lies underneath a menacing blanket of storm clouds on March 15, 2012.
The storm itself was insignificant, as weather events go, but the picture is fantastic.
Photo Credit: Jason Furda - DevineMayhem Studios.


Blame it on the Ice Age?

Seasonal ice and flooding in the Pittsburgh Region is not just a present-day phenomenon. Floods have been plaguing the region for nearly 20,000 years, since the last Ice Age. It was the time of the Wisconsin Glacial Episode, the last major advance of the continental glaciers. Wisconsin glaciation covered Canada, the Upper Midwest and New England. It radically altered the North American landscape north of the Ohio River.

Prior to the glaciers, the pre-historic Monongahela and Ohio rivers flowed northward into Lake Erie. They were joined northward by three streams that over time merged to become the Allegheny River. After the glaciers advanced into the region, the southern shores of Lake Erie became icebound. The streams and rivers flowing into the lake were forced to find other outlets.

The Last Ice Age
18,000 years ago

Gradually, huge pools formed at the stream mouths causing back flooding. In the vicinity of what is now Moundsville, West Virginia, the Ohio River began flowing towards the southwest. The Monongahela River had always flowed north, but because of the flooding in the Lake Erie area it began to drop its suspended silt into its lower reaches. When the ice cap began to melt and retreat northward, the Allegheny Basin filled with deposits of glacial sediment left by the ice sheet.

These glacial deposits contributed to the present problems of flooding. In some areas, these deposits are over 150 feet deep. The land reacted when the glacial pressure eased, elevating up to 350 feet in some areas. This upheaval formed the divide just south of Lake Erie and ever since has caused the drainage of the basin to be southward towards Pittsburgh and the fork of the three rivers.


Flood Stage - 24 feet

The river level at the fork of the Ohio generally hovers slightly above the 15 to 16 foot mark. Flood level at the Point is set at 24 feet. It's normal for Pittsburgh to reach flood stage at least once a year, either as the result of heavy winter snowfall or a warm weather low-pressure system that dumps an abnormally high amount of rainfall along the river basins.

The flooded Point on November 21, 2003
(river crest at 25.86 feet)    The Mon Wharf, which begins to flood at 18 feet,
 in March, 2010 (river crest at 22.6 feet).
Left - The Point in downtown Pittsburgh on November 21, 2003, when the river crested at 25.86 feet.
Right - The flooded Mon Wharf on March 14, 2010, with a river crest of 22.6 feet.

On November 21, 2003, the rivers crested at 25.86 feet. The Mon Wharf and the Allegheny Riverfront were submerged. The stretch of the Parkway East along the riverfront heading towards the Fort Pitt Tunnels, known as the bathtub, was submerged and the Point flooded up to the top of the steps leading to the fountain. The outer ring of the fountain was totally submerged and obscured from view, with only the elevated spout above the water level. This is the result of a rather average yearly flood, with water around two feet above flood level.

Now try to imagine what the result would be if the river waters rose to the level of thirty feet or more. It has happened over twenty-five times since the inhabitants of the city began charting river levels in the 1760s. Several of these floods have been devastating, with waters cresting above forty feet twice, in March of 1763 (41'0") and in March of 1936 (46'4").


The 100-Year Flood and the 500-Year Flood

Flood experts generally describe floods statistically. For example, some flooding is expected to occur on an average of one and a half years. Large, damaging floods occur statistically once every 100 years, and truly devastating floods occur once every 500 years.

In reality, floods occur at very irregular intervals, and the severity of flooding varies greatly as well. In downtown Pittsburgh, where the normal pool elevation of the three rivers is 710 feet above sea level (15 to 16 feet actual water depth), a 100-Year flood would raise the water level twenty feet (35 to 36 feet actual water depth). A 500-Year flood would increase the water level by an additional ten feet or more.

The 500-year flood of 1936
During the Great Saint Patrick's Day Flood of 1936 floodwaters
peaked at 46.4 feet. It was classified as a 500-Year Flood.

Despite the statistical infrequency, downtown Pittsburgh has suffered seven 100-Year floods (35+ feet) in the 20th Century alone. Many others rose to within a foot or two of the classification. The disastrous St. Patrick’s Day Flood of 1936, which peaked at over thirty feet above normal pool level (46'4" actual water depth), was a record-setting 500-Year flood and the worst to hit the Pittsburgh region.

Over the course of Pittsburgh's history, the city has been the scene of fifteen floods over the 35 foot level. That's fifteen 100-Year floods in 250 years. Luckily, due to the flood controls in place, the city has had only two 100-Year floods since 1942.


Attempts at Flood Control

After the Big Flood of 1907, Pittsburgh petitioned the government to begin the system of flood control measures. The Chamber of Commerce estimated that the persistent flooding had caused between $150,000,000 and $200,000,000 in damages to the city. The plans stalled.

The Big Flood of 1907. Liberty Avenue
 is submerged
The Big Flood of 1907 spurred local politicians to begin work on flood control measures.

Unfortunately, it took the St. Patrick's Day Flood twenty-six years later to spur the federal government to action. Within weeks of the disastrous 1936 flood, which totally obliterated the town of Johnstown, President Franklin Roosevelt signed into law a bill that would provide funds for the systems of dams, locks and reservoirs that now provide a measure of safety.

The development of flood controls has helped alleviate the worst flooding problems along the rivers. For example, record flooding during Hurricane Agnes in 1972 occurred in the upper Allegheny River drainage basin in New York and northern Pennsylvania. However, the severity of flooding was greatly reduced in Western Pennsylvania by the Kinzua Dam in McKean County and the locks and dams system along the river. A lot of water went downriver, but not nearly as much as would have if the controls were not in place. At the Point in Pittsburgh, river levels were estimated to be twelve feet lower because of the control system. Flood stage was estimated to be nearly thirteen feet lower during the flood of January, 1996.

The Kinzua Dam in McKee County    The locks and dam at Emsworth on the Ohio River,
five miles downriver from the city of Pittsburgh.
The Kinzua Dam (left) in McKee County and the Emsworth Locks and Dam. Flood control measures
like these have greatly reduced the severity of major flooding in the Pittsburgh region.

As effective as the controls are, however, even they cannot completely alleviate flooding problems. Man-made flood control systems are designed primarily to maintain floodwaters within a narrower area than they would cover naturally. To compensate for that part of the floodplain protected by the flood control system, backup of the floodwaters will occur, thus increasing the elevation of floodwaters upstream. Despite the threat to upstream dwellers, the system works.

Flood Control System
The system of flood control locks and dams built by the Army Corps of Engineers.

Perhaps the most convincing example of the effectiveness of these flood control measures occurred during the one-two punch of Hurricane Francis and Hurricane Ivan during the summer of 2004. Francis dumped a record rainfall amount of 3.60 inches, followed nine days later by Ivan, which surpassed that record by unleashing an incredible 5.95 inches on the already saturated region.

On September 19, 2004, the rivers crested at 31 feet. Although surrounding municipalities such as Carnegie suffered catastrophic consequences from overflowing creeks and tributaries, the downtown area was spared the full wrath of the rivers, relatively speaking. Although flooding was bad in the city, the consequences of such a tropical deluge could have been equal to or worse than the Great Flood of 1936.

For more statistical rainfall information: NOAA Precipitation Statistics for Pittsburgh.

Record Floods Over the Past 250 Years

31'0"
34'6"
35'8"
31'6"
32'4"
33'4"
36'6"
35'1"
32'4"
32'1"
46'4"
34'0"
30'4"
31'0"

 

2004, September 19
1996, January 20
1972, June 24
1964, March 11
1954, October 16
1945, March 7
1942, December 31
1937, April 26
1937, January 23
1936, March 19
1936, March 18
1936, March 17
1924, January 4
1913, January 9

38'7"
32'0"
35'6"
36'3"
36'5"
30'9"
31'9"
35'1"
38'2"
36'2"
35'2"
37'1"
41'0"
39'2"

 

1907, March 15
1904, January 23
1902, March 1
1901, April 20
1884, February 6
1861, September 21
1852, August 19
1852, April 19
1832, February 10
1816, February 15
1810, November 9
1806, April 10
1763, March 9
1762, January 9

  
Storm clouds over Brookline (left) and PNC Park on July 10, 2013 from a derecho that passed through Pittsburgh.
The heavy rains caused minor flooding along the three rivers, but disastrous flooding occured along tributaries
like Saw Mill Run Creek in South Park and Little Saw Mill Run along Banksville Road. The photos below
show flooding at the South Park Fairgrounds and along Banksville Road near the Parkway West.

Flooding along Saw Mill Run Creek
at the fairgrounds in South Park.    Flooding along Banksville Road
near the Parkway West exchange.


Other Disasters - Snowfalls, Tornados and Earthquakes

"Let It Snow, Let It Snow, Let It Snow"

It snows in Pittsburgh. That's a fact of life in the Midwest. Sometimes it snows quite a bit. A ten inch snowfall can temporarily paralyze the city, making life difficult for the local populace. Snowfalls exceeding one foot can cause serious disruption, and those approaching two feet can rival the damaging consequences of the 100-Year flood. Pittsburghers have experienced a four twenty-plus inch snowstorms since the late 1800s.

Bellaire Place in Brookline - February 6, 2010    Bellaire Place in Brookline - February 6, 2010
On February 6, 2010, residents on Bellaire Place in Brookline woke to a whopping 21.1 inches.

<Hazards Remain In Aftermath Of Massive Storm - February 7, 2010>

Most recently, on February 5th and 6th, 2010, the city was covered with a 21.1 inch blanket of the white stuff. Downed trees and power lines caused over 100,000 homes to lose power. Travel around the city was nearly impossible. Stranded vehicles dotted the roadways. After 24 hours the snowfall ceased and it was time to dig out. Residents often found their cars completely encased in a mound of snow. The National Guard was called in to assist municipal efforts. The storm generated the fourth highest snowfall amount on record in Pittsburgh.

The Boulevard of the Allies in downtown
Pittsburgh during the height storm.    The infamous parking chair. When the snow
builds up, the chairs mark your parking spot.
Some say this is a Pittsburgh tradition.
Left - The Boulevard of the Allies in downtown Pittsburgh during the February 2010 snowstorm.
Right - The Parking Chair. Clear the snow and mark your spot. Some love'm and some hate'm.
According to some historians, the use of the
Parking Chair began right here in Pittsburgh.

Three days later, on February 9th and the 10th, 2010, a second storm dropped 7.9 inches to increase the six-day total to 29.0 inches. Statistically, it was the second highest back-to-back (within two weeks of each other) storm total, replacing the 27.0 inches that fell in the dual storms of January 16th and January 21st, 1978. The snow continued to fall. By month's end, February 2010 (48.7 inches) had eclipsed January 1978 (40.2 inches) as the snowiest month ever in the city.

Brookline Boulevard - January 1978    Brookline Boulevard - January 1978
Brookline Boulevard on January 20, 1978, after the second major snowstorm in a week.

Another major snowstorm was the Blizzard of 1993, when for three days in March, snow fell without pause. When it was over, the total accumulation in Pittsburgh amounted to 25.3 inches and third place on the overall list. Nationally, the Nor'easter was called the Storm of the Century due to it's intensity, massive size and wide-reaching effect. The Superstorm stretched from Central America to Eastern Canada, affecting twenty-six states in the United States.

The second largest single blizzard total was recorded during a storm in mid-December of 1890, when the city was covered in a 25.9 inch blanket of fluff. A followup storm began one week later on Christmas Day which dumped an additional 13.2 inches, for a grand total of 39.1 inches. These two snowfalls together amounted to the largest back-to-back storm total in Pittsburgh weather history.

But, as terrible as these snowfalls were, they could not compare with the Granddaddy of all arctic snowstorms, the Thanksgiving Blizzard of 1950. Officially, 27.4 inches were recorded at the airport. Some neighborhoods, like Brookline, were buried in over thirty inches of snow. For three days, city workers labored to clear the streets and the National Guard was called upon to keep order in the paralyzed city.

Brookline Boulevard after the Blizzard of 1950    Trolley service ground to a halt
during the Thanksgiving Blizzard
Left - Automobile traffic on Brookline Boulevard the day after the blizzard - November 1950;
Right - Pittsburgh's public transportation ground to a halt during the Thanksgiving storm.

For more statistical snowfall information: NOAA Snowfall Statistics for Pittsburgh.


Brrrrrrrrrr!

Sometimes it's not so much the snow that poses the greatest risk during the snowy months. It's the bitter cold of winter that chills the heart and makes it difficult to travel, let alone go outside the front door. Frostbite can set quite quickly in subzero temperatures, and proper cold-weather clothing is essential for those who dare to brave the cold.

The longest recorded period of persistent sub-zero temperatures was a fifty-two hour stretch from January 18 through January 20, 1994. The lowest temperature on record in Pittsburgh, -22 degrees, was set during that cold spell, on January 19, 1994.

I lived in Columbus, Ohio at the time.
On January 19, 1994, at midnight this
picture was taken in my garage.  The
temperature in Columbus was -10 and
falling. That morning the thermometer
bottomed out at a frigid -20 degrees.

The longest period of sustained sub-freezing temperatures was a thirty-three day cold spell lasting from December 26, 1976 through January 27, 1977. Many Pittsburghers who were in elementary or high school during that blast of frigid weather were treated to an extended holiday vacation. Fuel oil was in short supply, it was the third snowiest January on record and the wind-chill was dangerously low. Many local area schools remained closed until February.

For historical information on cold weather: NOAA Pittsburgh Cold Weather Statistics.

Ice forms along the Allegheny River
during periods of bitter cold.    Ice forms along the Allegheny River
during periods of bitter cold.
Ice forms along the Allegheny River during periods of bitter cold.


Sometimes It Can Get Really Hot, Too

On the other side of the weather spectrum is the threat of high temperatures and prolonged heat waves. Like too much rain, too much heat can have devastating consequences and pose serious health risks to both young and old alike. When humidity is factored into temperatures above 90 degrees, Pittsburgh truly becomes a mid-western melting pot.

The highest temperature on record in Pittsburgh was set on July 16, 1988, when the thermometer peaked at 103 degrees. This was the third time in the City's history that the mercury reached that level, tying the record set on July 10, 1881 and again on August 6, 1918. Pittsburgh temperatures have hit 100 degrees or higher twenty times since 1871.

The hottest year on record was 1921, when the annual average reached 55.4 degrees. The warmest day was August 6, 1918, when the mean temperature averaged out at 92 degrees. As for cumulative 90 degree days and longest heat waves, 1988 was a record year, with thirty-eight days of temperatures at or above that level of mercury. Two of the three longest heat waves (temperature above 90 degrees) in the City's history were recorded that summer. For thirteen days, from July 4 to July 16, and again for ten days, from August 8 to August 17, Pittsburgher's roasted in the sweltering heat.

In a touch of bitter irony, after suffering through the Great Saint Patrick's Day Flood in March 1936, Pittsburghers endured the most intense heat wave in the City's history the following July 1936, when for eight consecutive days the temperatures hit 95, 101, 101, 94, 98, 93, 102 and 91 degrees.

The sun rises over Brookline Park on March 17, 2012.
The temperature that day reached 77 degrees. The
longest March heat wave on record was set that
month, with eleven straight days over 70 degrees.
The sun rises over the misty shroud covering Brookline Park on March 17, 2012.

If Global Warming has a signature, some might say the month of March, 2012, looked like the real thing. As monthly heat waves go, the eleven-day period from March 13 through March 23 shattered the previous March monthly mark of five consecutive days set in 1990. The 70-plus degree daily high temperatures were over thirty degrees above normal for that time of year. For the record, the month of March 2012 posted the highest March monthly average mean temperature ever (51.5 degrees) for the City of Pittsburgh.

For historical information on warm weather: NOAA Pittsburgh Warm Weather Statistics.


Twisters and Macro-Bursts

As the clock ticked towards the end of the 20th Century, a new atmospheric phenomenon burst onto the scene, causing further concern for weather weary Pittsburghers. Large and dangerous storms have begun to produce tornados and macro-bursts. Twisters are a fairly common occurrance north of the city in places like Butler County, but a Golden Triangle Twister is a true rarity. Prior to 1998, the last recorded tornado in Pittsburgh occurred near Lincoln Place in 1944. The last time downtown Pittsburgh suffered a direct hit was over a century ago, in January of 1889.

Pittsburgh dodged a bullet back on May 31, 1985, when a line of violent storms with multiple funnel clouds left 65 dead, destroyed 1,009 homes and caused an estimated $375 million in damage in Western Pennsylvania. The town of Wheatland, Pa was totally obliterated by the only F5 tornado ever recorded in the state of Pennsylvania. One funnel cloud associated with that storm system did touch down just north of Pittsburgh.

The Fujita Scale

Pittsburghers developed a certain sense of protection from the hills surrounding the city. Those hills would act as a barrier and keep Mother Nature's fury away. It was a false sense of security. Beginning in 1998, Pittsburgh has been the target of three twisters and a series of macro-bursts after a 54-year calm.

The first occurred on June 2, 1998, sixteen people were injured by a twister that touched down west of the city, then proceeded along the Parkway West towards Mount Washington. The tornado soon reached the city, and the overlook hillside was blanketed in a large black cloud. Moments later, when the cloud dissipated, stunned residents emerged to find several homes damaged along Grandview Avenue and surrounding streets. Roofs and walls were torn from several structures. Trees were uprooted and debris littered the area. Several large trees lining Herschel Field were sheared away, broken in half like twigs. The tornado was the first to breach the city limits in 109 years. It registered as an F1 on the Fujita Scale.

Tornado Damage - Mount Washington 1998       Tornado Damage - Mount Washington 1998
Governor Tom Ridge and Mayor Tom Murphy inspect damage in Mount Washington.

<Fronts created Tornado Alley> <> <Residents Weather Stormy Evening>
<Region Torn Asunder By Hard-Hitting Storms>

<><><><><><><><><> <><><><><><><><><> <><><><><><><><><>

On June 1, 2002, Kennywood Park in West Mifflin was the scene of a macro-burst that ripped the roof off of the pavilion covering The Whip, a ride in the Lost Kennywood section, hurling the structure onto a crowd of frightened onlookers. The powerful storm produced wind gusts registering over 80 mph. One person was killed and over fifty injured in the tragedy. Several trees in the historic Trolley Park were damaged or destroyed. The fierce storm also damaged buildings in Lawrenceville, Homestead, East End and Bloomfield.

Tornado Damage - Mount Washington 1998
Firefighters inspect damage in Kennywood Park.

<Kennywood Park Witnesses Describe Chaos at Whip Ride>
<Woman Dies in Kennywood Collapse as Fierce Storms Tear Through Region>

<><><><><><><><><> <><><><><><><><><> <><><><><><><><><>

A year later, on June 12, 2003, a strong thunderstorm produced a funnel cloud. The vortex travelled from Greentree to Mount Washington, as seen from Flagstaff hill in Schenley Park. The following day the National Weather Service confirmed that the funnel cloud was indeed an F0 tornado with 75 mph winds. It was Pittsburgh's second tornado in five years, but it would not be the last. The 2003 twister is shown in the photos below.

Tornado - Pittsburgh 2003    Tornado - Pittsburgh 2003 with the
Cathedral of Learning in foreground.
An F0 tornado that hit Greentree and Mount Washington photographed from Schenley Park in June 2003.

<Tornado-like Winds Fell Trees Throughout Region>
<Storm Damage Wasn't Too Bad, Considering It Was A Tornado>

<><><><><><><><><> <><><><><><><><><> <><><><><><><><><>

On August 9, 2007, a storm system blew through Pittsburgh and produced multiple funnel cloud sightings, accompanied by an 85 mph microburst in the Uptown district. In Sheraden, near Chartiers Avenue, trees were uprooted and projectile damage was done. An F-0 tornado was confirmed the following day by the National Weather Service.

<It's Official: Tornado Hit Sheraden>

Path of August 2007 tornado

<><><><><><><><><> <><><><><><><><><> <><><><><><><><><>

On June 17, 2009, a rapid series of powerful thunderstorms produced multiple funnel cloud sightings. The storms dumped over three inches of rain in some locations, causing severe flash flooding. On the University of Pittsburgh campus in Oakland, Forbes Avenue became a river, stranding several motorists in water that reached three feet deep in some areas.

<Big Storm Pummels The Region>

Although there were no confirmed reports of a tornado touch down, Becky Yeargers of Upper St. Clair snapped the photo below of a funnel cloud threatening the southern suburbs.

Flooding along Forbes Avenue,
near the Cathedral of Learning.
Post-Gazette Photo - 6/17/09      Funnel cloud sighted in Upper St. Clair
Flooding along Forbes Avenue in Oakland and a funnel cloud in Upper St. Clair - June 2009.

<><><><><><><><><> <><><><><><><><><> <><><><><><><><><>

Most recently, on March 23, 2011, a strong storm system ripped through the Pittsburgh area, dumping quarter-sized hail throughout the city. Fifteen miles to the west, the ominous clouds unleashed a tornado, packing 120 mile per hour winds, upon Westmoreland County. There were multiple reports of downed trees and power lines. Roofs were ripped off houses in Fort Allen, Hempfield and Irwin. Other areas that sustained heavy damage included Sewickley Township, North Huntingdon, Rillton and Herminie. The damage followed a line south from Route 30 to I-70, roughly along Route 136. The twister ranked an F-2 on the Fujita Scale, the strongest to hit the region in decades.

<Violent storm tears through Westmoreland, damages Hempfield Area High School>
<Tornado damage reaches $4M, 30 Hempfield homes destroyed along 7-mile path>

<Trib-Live Photo Slideshow of Tornado and Damage>

The tornado along Rt 30 in Hempfield.
Photo by Christian Hunter (from Post-Gazette).    Tornado in Hempfield Township.
The F2 tornado as seen by drivers along Route 30 in Hempfield Township on March 23, 2011.


"Did Somebody Say ... Earthquakes ???"

And last, but not least, who ever thought that the City of Pittsburgh was located in an earthquake prone area? Well, it is not. However, on March 1, 1935, the city did experience a slight tremor. That was one for the record books, until, on June 23, 2010, the city received another gentle nudge from a seismic event centered around Toronto, Canada. The Post-Gazette article below documents the 2010 magnitude 5.5 event.

<Canada-centered earthquake felt in Western Pennsylvania>

Seismographic reading -
 Pittsburgh, PA - 6/23/10.
Seismographic reading registered in Pittsburgh, Pennsylvania - 6/23/10.

<><><><><><><><><> <><><><><><><><><> <><><><><><><><><>

Most recently, on August 24, 2011, the City of Pittsburgh was shaken by another tremor, this one a 5.9 magnitude quake centered in Richmond, Virginia. This latest earthquake lasted nearly thirty seconds and caused buildings around the Pittsburgh area to shake, prompting numerous evacuations and some structural damage.

<Earthquake shakes region; buildings evacuated>

A damaged home on California Avenue - August 2011
Post-Gazette Photo    Seismographic readings showing horizontal
and vertical movement. August 24, 2011.
Bricks fell from this home on California Avenue (left) and seismographic readings from August 24, 2011.

Ironically, we can blame these tremors on the Ice Age also, as the earthquakes were likely caused by post-glacial rebound. The massive glaciers that descended upon North America exerted extreme downward pressure on the Earth's surface plates. These plates continue to slowly rebound upwards, a process that may take another 10,000 years.


The Calm After The Storm ... Rainbows Over Pittsburgh

A rainbow over Pittsburgh provides
a unique and scenic background
for Pirate fans at PNC Park.    A rainbow over Pittsburgh.

Not all inclement Pittsburgh weather has a negative outcome.
Sometimes a spring rain can have fascinating results.

A rainbow over Pittsburgh.    A rare double-rainbow over Pittsburgh.

On a hot summer day, the fountain at Point State Park can
be a refreshing treat, creating its own mini-rainbow.

The fountain at Point State Park is as
good as a spring shower on a hot day.

* Compiled from multiple sources - December 2004; Last Updated - August 25, 2013 *

<Historical Facts> <> <Brookline History>