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

Dangerous Heat and Heavy Rainfall into the Weekend

Hot temperatures and high humidity are forecast to continue across the mid-Mississippi Valley into this weekend. Heat Advisories remain in effect. Heavy to excessive rainfall occurring at times through the weekend could bring areas of flooding to parts of the northern Rockies, upper Midwest, central Great Lakes, and southern New England. Read More >

Current conditions at

Vance Brand Airport (KLMO)

Lat: 40.16°NLon: 105.16°WElev: 5039ft.

Fair

66°F

19°C

Humidity 72%
Wind Speed E 5 mph
Barometer 30.22 in
Dewpoint 57°F (14°C)
Visibility 7.00 mi
Last update 18 Sep 9:35 am MDT
Extended Forecast for

Longmont CO

  • Today

    Today: A slight chance of showers and thunderstorms between noon and 3pm, then showers likely and possibly a thunderstorm after 3pm. Partly sunny, with a high near 83. Calm wind becoming south southeast around 6 mph in the afternoon. Chance of precipitation is 60%.

    High: 83 °F

    Partly Sunny
    then Showers
    Likely

  • Tonight

    Tonight: A chance of showers and thunderstorms before 9pm, then a slight chance of showers between 9pm and midnight. Mostly cloudy, with a low around 54. West wind 5 to 8 mph becoming calm in the evening. Chance of precipitation is 50%.

    Low: 54 °F

    Chance
    Showers then
    Partly Cloudy

  • Saturday

    Saturday: Showers likely and possibly a thunderstorm between noon and 3pm, then a chance of showers and thunderstorms after 3pm. Increasing clouds, with a high near 78. Calm wind becoming east northeast around 5 mph in the afternoon. Chance of precipitation is 60%.

    High: 78 °F

    Mostly Sunny
    then Showers
    Likely

  • Saturday Night

    Saturday Night: Showers and possibly a thunderstorm. Low around 51. North wind around 5 mph becoming calm in the evening. Chance of precipitation is 80%.

    Low: 51 °F

    Showers then
    Chance
    Showers

  • Sunday

    Sunday: A chance of showers, with thunderstorms also possible after noon. Mostly cloudy, with a high near 74. Calm wind becoming northeast around 6 mph in the afternoon. Winds could gust as high as 15 mph. Chance of precipitation is 50%.

    High: 74 °F

    Chance
    Showers then
    Chance
    T-storms

  • Sunday Night

    Sunday Night: A chance of showers and thunderstorms before 9pm, then a chance of showers between 9pm and midnight. Partly cloudy, with a low around 48. Chance of precipitation is 30%.

    Low: 48 °F

    Chance
    Showers then
    Partly Cloudy

  • Monday

    Monday: Sunny, with a high near 75.

    High: 75 °F

    Sunny

  • Monday Night

    Monday Night: A slight chance of showers before midnight. Partly cloudy, with a low around 51.

    Low: 51 °F

    Slight Chance
    Showers then
    Partly Cloudy

  • Tuesday

    Tuesday: Mostly sunny, with a high near 77.

    High: 77 °F

    Mostly Sunny

Detailed Forecast

Today
A slight chance of showers and thunderstorms between noon and 3pm, then showers likely and possibly a thunderstorm after 3pm. Partly sunny, with a high near 83. Calm wind becoming south southeast around 6 mph in the afternoon. Chance of precipitation is 60%.
Tonight
A chance of showers and thunderstorms before 9pm, then a slight chance of showers between 9pm and midnight. Mostly cloudy, with a low around 54. West wind 5 to 8 mph becoming calm in the evening. Chance of precipitation is 50%.
Saturday
Showers likely and possibly a thunderstorm between noon and 3pm, then a chance of showers and thunderstorms after 3pm. Increasing clouds, with a high near 78. Calm wind becoming east northeast around 5 mph in the afternoon. Chance of precipitation is 60%.
Saturday Night
Showers and possibly a thunderstorm. Low around 51. North wind around 5 mph becoming calm in the evening. Chance of precipitation is 80%.
Sunday
A chance of showers, with thunderstorms also possible after noon. Mostly cloudy, with a high near 74. Calm wind becoming northeast around 6 mph in the afternoon. Winds could gust as high as 15 mph. Chance of precipitation is 50%.
Sunday Night
A chance of showers and thunderstorms before 9pm, then a chance of showers between 9pm and midnight. Partly cloudy, with a low around 48. Chance of precipitation is 30%.
Monday
Sunny, with a high near 75.
Monday Night
A slight chance of showers before midnight. Partly cloudy, with a low around 51.
Tuesday
Mostly sunny, with a high near 77.
Tuesday Night
A chance of showers before midnight. Mostly cloudy, with a low around 51.
Wednesday
Mostly sunny, with a high near 79.
Wednesday Night
Partly cloudy, with a low around 52.
Thursday
Mostly sunny, with a high near 81.
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ABOUT THIS FORECAST

 
Point Forecast:
Longmont CO
 40.16°N 105.09°W (Elev. 4980 ft)
Last Update:
12:46 am MDT Sep 18, 2026
Forecast Valid:
9am MDT Sep 18, 2026-6pm MDT Sep 24, 2026
 
Forecast Discussion
 
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Additional Resources

Radar & Satellite Image

Link to Local Radar Data Link to Satellite Data

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