Johnstown, CO Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Johnstown, a town in Weld County, Colorado.
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 for Johnstown
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Tonight | 54°F | Mostly Cloudy | 5 mph WNW | 8% |
| Saturday | 75°F | Partly Sunny then Chance Showers And Thunderstorms | 1 to 7 mph SSE | 73% |
| Saturday Night | 50°F | Showers And Thunderstorms Likely then Chance Showers And Thunderstorms | 2 to 7 mph NW | 55% |
| Sunday | 71°F | Chance Rain Showers | 2 to 6 mph NE | 54% |
| Sunday Night | 47°F | Chance Rain Showers then Partly Cloudy | 1 to 6 mph E | 28% |
| Monday | 72°F | Mostly Sunny | 1 to 6 mph SSE | 2% |
| Monday Night | 49°F | Slight Chance Rain Showers then Partly Cloudy | 2 to 7 mph NE | 16% |
| Tuesday | 77°F | Mostly Sunny | 5 mph NE | 8% |
| Tuesday Night | 52°F | Chance Showers And Thunderstorms then Mostly Cloudy | 6 mph NNW | 30% |
| Wednesday | 79°F | Mostly Sunny | 5 mph NE | 7% |
| Wednesday Night | 51°F | Slight Chance Rain Showers then Mostly Cloudy | 5 mph W | 15% |
| Thursday | 79°F | Mostly Sunny | 2 to 7 mph NNE | 9% |
| Thursday Night | 53°F | Slight Chance Rain Showers then Mostly Cloudy | 2 to 7 mph SSE | 17% |
| Friday | 79°F | Mostly Sunny | 2 to 7 mph E | 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
Nearby towns & communities
Aristocrat Ranchettes
Ault
Berthoud
Briggsdale
Dacono
Eaton
Erie
Evans
Firestone
Fort Lupton
Frederick
Garden City
Gilcrest
Greeley
Grover
Hudson
Keenesburg
Kersey
La Salle
Mead
Milliken
Nunn
Orchard
Pierce
Platteville
Raymer (New Raymer)
Severance
Windsor
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 Sep 19, 2026.