National Weather Service Forecast for: Johnstown CO
Issued by: National Weather Service Denver-Boulder, CO
Updated: 12:46 pm MDT Sep 12, 2026
 
Tonight

Tonight: Mostly clear, with a low around 55. North northwest wind 3 to 5 mph.
Mostly Clear

Sunday

Sunday: A chance of showers, with thunderstorms also possible after 3pm.  Increasing clouds, with a high near 92. Light and variable wind becoming southeast 6 to 11 mph in the afternoon. Winds could gust as high as 18 mph.  Chance of precipitation is 30%.
Sunny then
Chance
Showers
Sunday
Night
Sunday Night: A slight chance of showers and thunderstorms.  Mostly cloudy, with a low around 60. West southwest wind 5 to 9 mph becoming east northeast in the evening. Winds could gust as high as 15 mph.  Chance of precipitation is 20%.
Slight Chance
T-storms then
Slight Chance
Showers
Monday

Monday: A slight chance of showers between noon and 3pm, then a slight chance of showers and thunderstorms after 3pm.  Partly sunny, with a high near 87. Calm wind becoming southwest 5 to 7 mph in the afternoon.  Chance of precipitation is 20%.
Mostly Cloudy
then Slight
Chance
T-storms
Monday
Night
Monday Night: A 30 percent chance of showers, mainly after midnight.  Mostly cloudy, with a low around 54. North wind 5 to 11 mph, with gusts as high as 18 mph.
Chance
Showers

Tuesday

Tuesday: A slight chance of showers, then a chance of showers and thunderstorms after noon.  Partly sunny, with a high near 74. Chance of precipitation is 40%.
Chance
Showers

Tuesday
Night
Tuesday Night: A 40 percent chance of showers and thunderstorms before midnight.  Mostly cloudy, with a low around 53.
Chance
Showers then
Partly Cloudy
Wednesday

Wednesday: A slight chance of showers and thunderstorms after noon.  Mostly sunny, with a high near 82.
Mostly Sunny
then Slight
Chance
T-storms
Wednesday
Night
Wednesday Night: A chance of showers and thunderstorms before midnight, then a slight chance of showers.  Mostly cloudy, with a low around 54.
Chance
Showers

Lo 55 °F Hi 92 °F Lo 60 °F Hi 87 °F Lo 54 °F Hi 74 °F Lo 53 °F Hi 82 °F Lo 54 °F

 

Tonight
 
Mostly clear, with a low around 55. North northwest wind 3 to 5 mph.
Sunday
 
A chance of showers, with thunderstorms also possible after 3pm. Increasing clouds, with a high near 92. Light and variable wind becoming southeast 6 to 11 mph in the afternoon. Winds could gust as high as 18 mph. Chance of precipitation is 30%.
Sunday Night
 
A slight chance of showers and thunderstorms. Mostly cloudy, with a low around 60. West southwest wind 5 to 9 mph becoming east northeast in the evening. Winds could gust as high as 15 mph. Chance of precipitation is 20%.
Monday
 
A slight chance of showers between noon and 3pm, then a slight chance of showers and thunderstorms after 3pm. Partly sunny, with a high near 87. Calm wind becoming southwest 5 to 7 mph in the afternoon. Chance of precipitation is 20%.
Monday Night
 
A 30 percent chance of showers, mainly after midnight. Mostly cloudy, with a low around 54. North wind 5 to 11 mph, with gusts as high as 18 mph.
Tuesday
 
A slight chance of showers, then a chance of showers and thunderstorms after noon. Partly sunny, with a high near 74. Chance of precipitation is 40%.
Tuesday Night
 
A 40 percent chance of showers and thunderstorms before midnight. Mostly cloudy, with a low around 53.
Wednesday
 
A slight chance of showers and thunderstorms after noon. Mostly sunny, with a high near 82.
Wednesday Night
 
A chance of showers and thunderstorms before midnight, then a slight chance of showers. Mostly cloudy, with a low around 54.
Thursday
 
A chance of showers, with thunderstorms also possible after noon. Partly sunny, with a high near 75.
Thursday Night
 
A chance of showers. Mostly cloudy, with a low around 52.
Friday
 
A slight chance of showers and thunderstorms. Mostly sunny, with a high near 79.
Friday Night
 
A slight chance of showers. Partly cloudy, with a low around 51.
Saturday
 
Mostly sunny, with a high near 78.

 

Forecast from NOAA-NWS for Johnstown CO.