Chester County

Every recorded tornado

1. Injuries and deaths are for the tornado’s whole path, which may extend beyond the county. Deaths recorded within Chester County: 2.
2. Weak tornadoes were under-recorded before Doppler radar coverage became national in the early 1990s, so earlier decades read low. Ratings use the Fujita scale before February 2007 and the Enhanced Fujita scale after.

Storm Prediction Center severe weather database, 1950 to 2025.

Every storm within 100 miles

1. Tropical storms and hurricanes (34 kt or more, still tropical) at closest approach. Post-tropical remnants with gale-force winds are listed but not counted. Direct: track within 50 miles; near: within 100 miles. Distance is measured to the county boundary for counties and to the city centre for cities, using positions interpolated hourly between HURDAT2 fixes.

National Hurricane Center HURDAT2, 1851 to 2025.

Every large fire

1. Large fires mapped by the Monitoring Trends in Burn Severity program since 1984: 1,000 acres or more in the West, 500 or more in the East. Prescribed burns are excluded. Acres here are the part of each perimeter inside this place.

Monitoring Trends in Burn Severity (USGS and U.S. Forest Service), 1984 to 2026.

Smoke overhead

1. A smoke day is a date on which a smoke plume traced by NOAA Hazard Mapping System analysts from satellite imagery covered this place's point (the county's population centre or the city centre). Counts here are of medium or heavy smoke. Since 2018 analysts have often drawn light smoke as one area over most of the continent, so light-smoke counts are not comparable from year to year. The plumes show smoke anywhere in the air above, not air quality at the ground, and smoke hidden by cloud is missed.

NOAA Hazard Mapping System smoke analysis, 2011 to 2026, retrieved October 30, 2026.

Claims by ZIP code

This product uses the Federal Emergency Management Agency's OpenFEMA API, but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).

OpenFEMA NFIP Redacted Claims v3, refreshed August 4, 2026. NOAA Storm Events through 2026.

River crests

River gauges

1. Crests are the highest and the recent crests the National Weather Service lists for each river gauge in the county that has a flood stage, not every flood. Flood categories use each gauge's current flood stages; crests from before levees, dams or channel changes may not be comparable. Crests measured on an old datum are left out of the rankings.

NOAA National Water Prediction Service gauge records, retrieved October 30, 2026.

1. The Palmer Drought Severity Index is computed by NOAA each month from the county's average temperature and precipitation, relative to the county's own climate. Zero is normal; -3 or lower is severe drought and -4 or lower extreme drought. It describes the long-term balance of moisture, not water supply or crop losses.

NOAA NCEI nClimDiv county Palmer Drought Severity Index, 1895 to September 2026, issued October 6, 2026.

Every earthquake of magnitude 4 or more within 50 miles

1. Earthquakes of magnitude 2.5 or more in the USGS Comprehensive Catalog since 1900. Within 50 miles means the epicentre lies within 50 miles of the county boundary (or inside the county).
2. Small earthquakes were under-recorded before the modern seismic networks of the 1970s and are still missed in remote areas, so early decades read low. Magnitudes are as the catalogue reports them and mix scales (moment, local and body-wave).

USGS ANSS Comprehensive Earthquake Catalog, 1900 to present, retrieved October 30, 2026.

More event types since 1996

Costliest events since 1996

1. Sep 1, 2021Flash Flood$40.0 million
   National Weather Service narrative

   Widespread flash flooding occurred in Chester County with many road closures and vehicles stranded. There was a flood related fatality in Downingtown. Numerous waterways in the county flooded, including the Schuylkill River, the West Branch of the Brandywine Creek, the East Branch of the Brandywine Creek, White Clay Creek, Red Clay Creek, French Creek and Valley Creek. There were many reports of water entering buildings and homes.

2. Sep 18, 2003High Wind, Chester$6.7 million
   National Weather Service narrative

   Tropical Storm Isabel produced strong power outage producing winds, moderate tidal flooding along the Delaware River and stream flooding in Chester County. Isabel made landfall as a hurricane near Drum Inlet, North Carolina around 100 p.m. EDT on the 18th and weakened as it tracked farther inland. At one time in its life cycle, it was a powerful Category 5 hurricane when it was north of the Leewood Islands. Winds gusted up to 60 mph in Eastern Pennsylvania and downed countless numbers of trees, tree limbs and power lines. It was the worst outage on record for PECO Energy in southeastern Pennsylvania. About 572,425 of its customers lost power. This exceeded the outages that…

3. Jun 27, 2006Flood$6.0 million
   National Weather Service narrative

   Several days of heavy rain throughout Southeastern Pennsylvania culminated with major flooding along the Brandywine Basin and moderate flooding along Schuylkill River from the 27th through the 29th. President George W. Bush declared Chester County a disaster area. Sporadic periods of heavy rain started on the 23rd, but the most widespread and heaviest rain fell from the night of the 27th into the morning of the 28th. During bursts of heavier rain on the 28th, flash flooding of smaller streams occurred and the ongoing flooding along the main stem rivers was exacerbated. Event totals in Chester County averaged six to twelve inches.Governor Ed Rendell declared a disaster emergency in…

4. Feb 9, 2010Winter Storm, Chester$5.0 million
   National Weather Service narrative

   For the second time within a week a major winter storm affected Eastern Pennsylvania on the 10th and 11th and smashed seasonal snowfall records in the Philadelphia area. Snowfall averaged one to two feet with some locally higher amounts in the Philadelphia northwest suburbs. ||Around the local Philadelphia area, snow began during the early evening on the 9th. As warmer air moved in aloft, the snow changed to sleet and freezing rain between 3 a.m. and 6 a.m. EST on the 10th. Surface temperatures responded slower and the sleet and freezing rain changed over to rain during the morning of the 10th. Some sleet mixed in from time to time. As the low pressure system moved northeast of…

5. Sep 15, 2003Flash Flood$3.5 million
   National Weather Service narrative

   Remnant moisture from Tropical Storm Henri produced copious amounts of rain during the early morning of the 15th across Chester County. The heaviest rain fell from Downingtown south through Kenneth Square. Thunderstorms with torrential downpours moved from south to north across the same areas and produced five to ten inches of rain across the region. The worst flood damage occurred in Avondale, Downingtown and Kenneth Square. During the flooding there were 2,600 emergency calls to the county 911 center. Over half required dispatches. There were 100 water rescues from vehicles and homes. Twelve homes were destroyed. One hundred eighty homes suffered major damage. One hundred…

6. Nov 26, 1999Tornado$3.0 million
   National Weather Service narrative

   An unseasonably warm and humid air mass and an approaching cold front combined to produce a tornado (F1 on the Fujita Scale) in Honey Brook near 6 p.m. EST. About a dozen people were injured. Two barns and four houses were destroyed, twenty-five other homes were damaged. A warehouse was also badly damaged. About 35 families were evacuated. Damage was estimated at 3 million dollars. Based on the storm survey, winds were near the high range of the F1 tornado scale and were estimated to be around 100 mph.The tornado touched down near Diane Drive then moved on a north path paralleling Pennsylvania State Route 10 and crossed U.S. Route 322 near the Zook's Molasses Warehouse. The…

7. Sep 16, 1999Flash Flood$3.0 million
   National Weather Service narrative

   Hurricane Floyd battered Eastern Pennsylvania (especially Southeast sections around Philadelphia) on September 16th and brought with it torrential and in some places record breaking rains and damaging winds. The hurricane caused widespread flash flooding as storm totals averaged around six inches in the Poconos and Berks County, eight inches in the Lehigh Valley and from eight to twelve inches in the Greater Philadelphia Metropolitan Area. Six people died directly from the hurricane - four drownings and two persons were hit by trees. The hurricane also indirectly contributed to the death of about seven other persons. About 40 persons were seriously injured. There were hundreds of…

8. Jan 7, 1996Blizzard, Chester$2.2 million
   National Weather Service narrative

   The Blizzard of '96, the second coined "STORM OF THE CENTURY" of this decade brought record breaking snow to most of Southeast Pennsylvania and paralyzed the region for several days, caused most municipalities to exceed their annual snow budgets during this one storm, caused several building collapses and caused directly or directly 42 deaths and countless injuries. Six persons died of hypothermia, 4 in Philadelphia, 1 in Delaware County and 1 in Lehigh County. Some were homeless persons, but one woman in Allentown accidentally locked herself out of her home. Twenty-nine persons suffered heart attacks and died while shoveling snow, using snowblowers or trying to walk in the deep…

9. Sep 16, 1999High Wind, Chester$2.0 million
   National Weather Service narrative

   Hurricane Floyd battered Eastern Pennsylvania (especially Southeast sections around Philadelphia) on September 16th and brought with it torrential and in some places record breaking rains and damaging winds. The hurricane caused widespread flash flooding as storm totals averaged around six inches in the Poconos and Berks County, eight inches in the Lehigh Valley and from eight to twelve inches in the Greater Philadelphia Metropolitan Area. Six people died directly from the hurricane - four drownings and two persons were hit by trees. The hurricane also indirectly contributed to the death of about seven other persons. About 40 persons were seriously injured. There were hundreds of…

10. Apr 30, 2014Flood$1.4 million
    National Weather Service narrative

    Very heavy rain caused widespread poor drainage and moderate to major creek and river flooding throughout Chester County. Two apartment complexes had to be evacuated. Over one hundred roadways were flooded and closed. More than sixty-five people were rescued from trapped vehicles. Three people trapped in their homes by flood waters were rescued. Flooding along the main stem of the Brandywine Creek was the worst since Tropical Storm Floyd on September 16, 1999. Other flooding was the worst since Tropical Storm Irene on August 28, 2011. | |In Avondale Borough, flooding along the East Branch of the White Clay Creek forced the evacuation of 300 residents in the Avondale Apartments on…

1. Storm Events records before 1996 cover only tornadoes, thunderstorm wind and hail. Damage figures are as reported by the National Weather Service at the time, not adjusted for inflation.

NOAA NCEI Storm Events Database, 1950 to 2026, issued October 26, 2026.

All-time high

103°F3 times, most recently Jul 2, 2026

All-time low

−14°F2 times, most recently Jan 21, 1985

Warmest night

82°FJul 22, 2011

Coldest day

4°FJan 19, 1994

Wettest day

8.29 inSep 16, 1999

Snowiest day

22.0 inJan 7, 1996

Hottest year

2023mean 57.8°F

Coldest year

1958mean 52.1°F

Wettest year

201861.37 in

Driest year

196524.90 in

Snowiest season

72.7 in2009-10

Station Wilmington New Castle County Airport (USW00013781), 74 ft elevation, 22.4 miles from the population centre. Daily records from 1931 to October 26, 2026; 100.0% of days in the last 30 years are complete. Records at a single station can differ from a city’s official threaded record, which may combine several stations.

NOAA NCEI Global Historical Climatology Network Daily.

This product uses the Federal Emergency Management Agency's OpenFEMA API, but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).

OpenFEMA Disaster Declarations Summaries, retrieved October 30, 2026. Statewide declarations are not listed.

Neighbouring counties

• Tornadoes NOAA Storm Prediction Center severe weather database, through 2025.
• Tropical cyclones NOAA National Hurricane Center HURDAT2 (Atlantic; Northeast and Central Pacific), through 2025.
• Wildfire USGS/USFS Monitoring Trends in Burn Severity, through 2026.
• Storm events NOAA NCEI Storm Events Database, through 2026.
• Flood insurance OpenFEMA NFIP Redacted Claims v3, refreshed August 4, 2026.
• Declarations OpenFEMA Disaster Declarations Summaries v2, retrieved October 30, 2026.
• Weather records NOAA NCEI Global Historical Climatology Network Daily, station USW00013781.
• River crests NOAA National Weather Service, National Water Prediction Service river gauges, retrieved October 30, 2026.
• Drought NOAA NCEI nClimDiv county Palmer Drought Severity Index, through September 2026.
• Smoke NOAA NESDIS Hazard Mapping System smoke analysis, retrieved October 30, 2026.
• Earthquakes USGS ANSS Comprehensive Earthquake Catalog (ComCat), retrieved October 30, 2026.

Joins, thresholds and known limits are set out in the methodology. Found an error? Report it. Page built October 30, 2026.