Longmont, CO Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Longmont, a city in Boulder County, Colorado.
This Afternoon
57°F
Sunny
Sunny. High near 57, with temperatures falling to around 53 in the afternoon. East northeast wind around 3 mph.
7-day forecast for Longmont
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| This Afternoon | 57°F | Sunny | 3 mph ENE | 0% |
| Tonight | 34°F | Mostly Clear | 3 mph SW | 0% |
| Wednesday | 57°F | Mostly Sunny | 0 to 3 mph NE | 6% |
| Wednesday Night | 35°F | Mostly Cloudy | 3 mph NNW | 6% |
| Thursday | 59°F | Sunny | 3 mph SSE | 0% |
| Thursday Night | 35°F | Partly Cloudy | 1 mph W | 1% |
| Friday | 58°F | Mostly Sunny | 1 to 5 mph SSE | 6% |
| Friday Night | 34°F | Mostly Clear | 2 mph SW | 6% |
| Saturday | 60°F | Sunny | 1 to 5 mph S | 0% |
| Saturday Night | 34°F | Mostly Clear | 2 mph WSW | 0% |
| Sunday | 66°F | Sunny | 2 mph SSW | 0% |
| Sunday Night | 39°F | Mostly Clear | 1 to 5 mph W | 0% |
| Monday | 66°F | Mostly Sunny | 3 mph SE | 0% |
| Monday Night | 39°F | Partly Cloudy | 2 mph NW | 0% |
Forecast source: National Weather Service (api.weather.gov) for Longmont (40.170, -105.102). Updated through the day.
Growing snapshot for Longmont
Last spring frost
May 7
First fall frost
Oct 5
Growing season
151 days
Hardiness zone
5b
More local growing data for Longmont: nearby ZIP 80501 weather · frost dates · planting calendar · Colorado frost dates
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Climate data from the nearest NOAA station, Longmont 2 Ese, Co (1.3 mi from Longmont). Frost dates are 1991–2020 averages, not a forecast. Page updated Nov 4, 2026.