National Oceanic and Atmospheric Administration National Weather Service United States Department of Commerce

Severe Thunderstorms in the Midwest and Arizona; Heat Continues in the Southeast and Southwest

Thunderstorms, some severe, may lead to scattered instances of flash flooding across the Midwest and Ohio Valley and southern Arizona. The threat will shift to the Mid-Atlantic coast on Thursday. Dangerous heat persists in the South and Southeast while building into the Southwest. Overnight lows will be so warm that little-to-no relief from the scorching daytime highs will be available. Read More >

Hazardous Weather Conditions

Current conditions at

Chester County Airport (KMQS)

Lat: 39.98°NLon: 75.87°WElev: 659ft.

Mostly Cloudy

69°F

21°C

Humidity 100%
Wind Speed Calm
Barometer 30.01 in
Dewpoint 69°F (21°C)
Visibility 9.00 mi
Last update 20 Aug 7:35 am EDT
Extended Forecast for

Exton PA

Flood Watch August 20, 12:00pm until August 21, 02:00am
Click here for hazard details and duration
Flood Watch

  • Today

    Today: Showers and thunderstorms, mainly after 2pm. High near 79. Calm wind becoming east around 5 mph in the afternoon. Chance of precipitation is 90%. New rainfall amounts between a half and three quarters of an inch possible.

    High: 79 °F

    Slight Chance
    T-storms then
    T-storms

  • Tonight

    Tonight: Showers and thunderstorms likely, mainly before 8pm. Patchy fog between 4am and 5am. Otherwise, mostly cloudy, with a low around 61. North wind around 5 mph. Chance of precipitation is 60%. New precipitation amounts between a quarter and half of an inch possible.

    Low: 61 °F

    T-storms
    Likely then
    Patchy Fog

  • Friday

    Friday: Patchy fog before 7am. Otherwise, mostly sunny, with a high near 78. North wind around 5 mph.

    High: 78 °F

    Patchy Fog
    then Mostly
    Sunny

  • Friday Night

    Friday Night: A chance of showers before 11pm, then a chance of showers and thunderstorms between 11pm and 2am, then showers likely and possibly a thunderstorm after 2am. Increasing clouds, with a low around 64. East wind around 5 mph becoming calm. Chance of precipitation is 60%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

    Low: 64 °F

    Chance
    Showers then
    Showers
    Likely

  • Saturday

    Saturday: Showers likely and possibly a thunderstorm. Mostly cloudy, with a high near 78. East wind around 5 mph. Chance of precipitation is 70%. New rainfall amounts between a quarter and half of an inch possible.

    High: 78 °F

    Showers
    Likely

  • Saturday Night

    Saturday Night: A chance of showers and thunderstorms before 11pm, then a chance of showers between 11pm and 2am. Mostly cloudy, with a low around 64. Chance of precipitation is 50%. New precipitation amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

    Low: 64 °F

    Chance
    T-storms then
    Chance
    Showers

  • Sunday

    Sunday: A chance of showers after 2pm. Partly sunny, with a high near 81. Chance of precipitation is 40%.

    High: 81 °F

    Partly Sunny
    then Chance
    Showers

  • Sunday Night

    Sunday Night: A chance of showers before 8pm. Partly cloudy, with a low around 61. Chance of precipitation is 30%.

    Low: 61 °F

    Chance
    Showers then
    Mostly Clear

  • Monday

    Monday: Sunny, with a high near 79.

    High: 79 °F

    Sunny

Detailed Forecast

Today
Showers and thunderstorms, mainly after 2pm. High near 79. Calm wind becoming east around 5 mph in the afternoon. Chance of precipitation is 90%. New rainfall amounts between a half and three quarters of an inch possible.
Tonight
Showers and thunderstorms likely, mainly before 8pm. Patchy fog between 4am and 5am. Otherwise, mostly cloudy, with a low around 61. North wind around 5 mph. Chance of precipitation is 60%. New precipitation amounts between a quarter and half of an inch possible.
Friday
Patchy fog before 7am. Otherwise, mostly sunny, with a high near 78. North wind around 5 mph.
Friday Night
A chance of showers before 11pm, then a chance of showers and thunderstorms between 11pm and 2am, then showers likely and possibly a thunderstorm after 2am. Increasing clouds, with a low around 64. East wind around 5 mph becoming calm. Chance of precipitation is 60%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.
Saturday
Showers likely and possibly a thunderstorm. Mostly cloudy, with a high near 78. East wind around 5 mph. Chance of precipitation is 70%. New rainfall amounts between a quarter and half of an inch possible.
Saturday Night
A chance of showers and thunderstorms before 11pm, then a chance of showers between 11pm and 2am. Mostly cloudy, with a low around 64. Chance of precipitation is 50%. New precipitation amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.
Sunday
A chance of showers after 2pm. Partly sunny, with a high near 81. Chance of precipitation is 40%.
Sunday Night
A chance of showers before 8pm. Partly cloudy, with a low around 61. Chance of precipitation is 30%.
Monday
Sunny, with a high near 79.
Monday Night
Mostly clear, with a low around 60.
Tuesday
Sunny, with a high near 79.
Tuesday Night
Mostly clear, with a low around 61.
Wednesday
A chance of showers. Mostly sunny, with a high near 81. Chance of precipitation is 30%.
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Forecast Area
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ABOUT THIS FORECAST

 
Point Forecast:
Exton PA
 40.03°N 75.61°W (Elev. 394 ft)
Last Update:
4:08 am EDT Aug 20, 2026
Forecast Valid:
7am EDT Aug 20, 2026-6pm EDT Aug 26, 2026
 
Forecast Discussion
 
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Additional Resources

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Hourly Weather Forecast

National Digital Forecast Database

National Digital Forecast Database Maximum Temperature Forecast

High Temperature

National Digital Forecast Database Weather Element Forecast

Chance of Precipitation