Johnstown, CO Weather & Growing Conditions
Tonight
54°F
Mostly Cloudy
Mostly cloudy, with a low around 54. West northwest wind around 5 mph. New rainfall amounts less than a tenth of an inch possible.
7-day forecast
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Tonight | 54°F | Mostly Cloudy | 5 mph WNW | 8% |
| Saturday | 76°F | Partly Sunny then Chance Showers And Thunderstorms | 1 to 7 mph SE | 73% |
| Saturday Night | 50°F | Chance Showers And Thunderstorms | 2 to 6 mph NW | 54% |
| Sunday | 71°F | Showers And Thunderstorms Likely | 5 mph NE | 55% |
| Sunday Night | 48°F | Chance Rain Showers then Partly Cloudy | 1 to 5 mph E | 27% |
| Monday | 72°F | Mostly Sunny | 1 to 6 mph SSE | 2% |
| Monday Night | 49°F | Slight Chance Rain Showers then Partly Cloudy | 2 to 6 mph NE | 15% |
| Tuesday | 77°F | Mostly Sunny | 5 mph NE | 8% |
| Tuesday Night | 52°F | Chance Showers And Thunderstorms then Mostly Cloudy | 5 mph N | 30% |
| Wednesday | 79°F | Partly Sunny | 5 mph NE | 7% |
| Wednesday Night | 52°F | Slight Chance Rain Showers then Mostly Cloudy | 5 mph WNW | 15% |
| Thursday | 79°F | Mostly Sunny | 2 to 7 mph NE | 9% |
| Thursday Night | 53°F | Slight Chance Rain Showers then Mostly Cloudy | 2 to 7 mph SSW | 17% |
| Friday | 80°F | Mostly Sunny | 2 to 6 mph ENE | 12% |
Forecast source: National Weather Service (api.weather.gov). Updated through the day.
Growing snapshot for Johnstown, CO
Last spring frost
May 10
First fall frost
Oct 1
Growing season
142 days
Hardiness zone
5b
Explore more for Johnstown, CO: full frost dates · planting calendar · Colorado frost dates
Climate data from the nearest NOAA station, Loveland 2N, Co (10.5 mi). Frost dates are 1991–2020 averages, not a forecast. Page updated Sep 19, 2026.