Johnstown, CO Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Johnstown, a town in Weld County, Colorado.
Today
78°F
Patchy Smoke
Patchy smoke. Mostly sunny. High near 78, with temperatures falling to around 76 in the afternoon. East wind 8 to 12 mph, with gusts as high as 18 mph.
7-day forecast for Johnstown
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Today | 78°F | Patchy Smoke | 8 to 12 mph E | 7% |
| Tonight | 55°F | Patchy Smoke | 6 to 12 mph ENE | 8% |
| Wednesday | 86°F | Patchy Smoke | 6 to 10 mph ENE | 0% |
| Wednesday Night | 57°F | Patchy Smoke then Mostly Clear | 5 to 12 mph NE | 1% |
| Thursday | 96°F | Sunny | 3 to 8 mph N | 0% |
| Thursday Night | 60°F | Mostly Clear | 5 to 9 mph N | 1% |
| Friday | 98°F | Sunny | 2 to 9 mph SW | 0% |
| Friday Night | 62°F | Mostly Clear | 5 to 9 mph S | 0% |
| Saturday | 100°F | Sunny | 2 to 9 mph NE | 2% |
| Saturday Night | 62°F | Partly Cloudy | 5 to 10 mph WNW | 1% |
| Sunday | 99°F | Sunny | 3 to 9 mph NNW | 6% |
| Sunday Night | 64°F | Partly Cloudy | 5 to 10 mph WNW | 6% |
| Monday | 98°F | Sunny | 5 to 13 mph NNE | 13% |
| Monday Night | 64°F | Mostly Cloudy | 5 to 15 mph NW | 12% |
Forecast source: National Weather Service (api.weather.gov) for Johnstown (40.307, -104.911). Updated through the day.
Growing snapshot for Johnstown
Last spring frost
May 10
First fall frost
Oct 1
Growing season
142 days
Hardiness zone
5b
More local growing data for Johnstown: nearby ZIP 80534 weather · frost dates · planting calendar · Colorado frost dates
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Severance
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Climate data from the nearest NOAA station, Loveland 2N, Co (10.5 mi from Johnstown). Frost dates are 1991–2020 averages, not a forecast. Page updated Aug 4, 2026.