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 >

Current conditions at

The Florida Keys - Marathon International Airport (KMTH)

Lat: 24.73°NLon: 81.05°WElev: 13ft.

Fair

87°F

31°C

Humidity 75%
Wind Speed Vrbl 3 mph
Barometer 30.00 in (1015.8 mb)
Dewpoint 78°F (26°C)
Visibility 10.00 mi
Heat Index100°F (38°C)
Last update 20 Aug 1:53 am EDT
Extended Forecast for

Marathon FL

  • Overnight

    Overnight: Mostly cloudy, with a low around 83. Northwest wind around 5 mph.

    Low: 83 °F

    Mostly Cloudy

  • Thursday

    Thursday: Partly sunny, with a high near 90. West wind around 5 mph.

    High: 90 °F

    Partly Sunny

  • Thursday Night

    Thursday Night: Partly cloudy, with a low around 83. Light and variable wind becoming southeast 5 to 10 mph after midnight.

    Low: 83 °F

    Partly Cloudy

  • Friday

    Friday: Mostly sunny, with a high near 89. South wind around 5 mph.

    High: 89 °F

    Mostly Sunny

  • Friday Night

    Friday Night: Partly cloudy, with a low around 83. Southeast wind 5 to 10 mph.

    Low: 83 °F

    Partly Cloudy

  • Saturday

    Saturday: Sunny, with a high near 90.

    High: 90 °F

    Sunny

  • Saturday Night

    Saturday Night: Mostly clear, with a low around 83.

    Low: 83 °F

    Mostly Clear

  • Sunday

    Sunday: Sunny, with a high near 89.

    High: 89 °F

    Sunny

  • Sunday Night

    Sunday Night: A slight chance of showers and thunderstorms. Mostly clear, with a low around 83. Chance of precipitation is 20%.

    Low: 83 °F

    Slight Chance
    T-storms

Detailed Forecast

Overnight
Mostly cloudy, with a low around 83. Northwest wind around 5 mph.
Thursday
Partly sunny, with a high near 90. West wind around 5 mph.
Thursday Night
Partly cloudy, with a low around 83. Light and variable wind becoming southeast 5 to 10 mph after midnight.
Friday
Mostly sunny, with a high near 89. South wind around 5 mph.
Friday Night
Partly cloudy, with a low around 83. Southeast wind 5 to 10 mph.
Saturday
Sunny, with a high near 90.
Saturday Night
Mostly clear, with a low around 83.
Sunday
Sunny, with a high near 89.
Sunday Night
A slight chance of showers and thunderstorms. Mostly clear, with a low around 83. Chance of precipitation is 20%.
Monday
Sunny, with a high near 90.
Monday Night
A chance of showers and thunderstorms. Mostly clear, with a low around 83. Chance of precipitation is 40%.
Tuesday
A slight chance of showers and thunderstorms. Mostly sunny, with a high near 89. Chance of precipitation is 20%.
Tuesday Night
A chance of showers and thunderstorms. Partly cloudy, with a low around 83. Chance of precipitation is 50%.
Wednesday
A slight chance of showers and thunderstorms. Mostly sunny, with a high near 89. Chance of precipitation is 20%.
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Forecast Area
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ABOUT THIS FORECAST

 
Point Forecast:
Marathon FL
 24.72°N 81.1°W (Elev. 0 ft)
Last Update:
2:15 am EDT Aug 20, 2026
Forecast Valid:
2am 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