Longmont, CO Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Longmont, a city in Boulder County, Colorado.
Today
76°F
Partly Sunny then Chance Showers And Thunderstorms
A chance of showers and thunderstorms between noon and 3pm, then showers and thunderstorms likely. Partly sunny. High near 76, with temperatures falling to around 70 in the afternoon. Northeast wind 2 to 7 mph. Chance of precipitation is 60%. New rainfall amounts between a tenth and quarter of an inch possible.
7-day forecast for Longmont
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Today | 76°F | Partly Sunny then Chance Showers And Thunderstorms | 2 to 7 mph NE | 60% |
| Tonight | 51°F | Chance Showers And Thunderstorms then Partly Cloudy | 1 to 5 mph NNW | 39% |
| Sunday | 72°F | Partly Sunny then Chance Showers And Thunderstorms | 1 to 6 mph NE | 29% |
| Sunday Night | 49°F | Chance Showers And Thunderstorms then Partly Cloudy | 0 to 5 mph NNW | 29% |
| Monday | 73°F | Sunny | 0 to 6 mph NE | 2% |
| Monday Night | 50°F | Slight Chance Showers And Thunderstorms then Partly Cloudy | 1 to 5 mph NNE | 15% |
| Tuesday | 76°F | Mostly Sunny | 3 mph NE | 6% |
| Tuesday Night | 52°F | Slight Chance Showers And Thunderstorms then Partly Cloudy | 2 mph NW | 18% |
| Wednesday | 78°F | Mostly Sunny | 3 mph NNE | 10% |
| Wednesday Night | 52°F | Partly Cloudy | 3 mph NW | 13% |
| Thursday | 80°F | Mostly Sunny | 2 to 6 mph NNE | 6% |
| Thursday Night | 54°F | Partly Cloudy | 1 to 5 mph SSW | 11% |
| Friday | 80°F | Mostly Sunny | 1 to 5 mph SE | 11% |
| Friday Night | 54°F | Slight Chance Rain Showers then Partly Cloudy | 3 mph SW | 16% |
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
Nearby towns & communities
Allenspark
Altona
Bark Ranch
Bonanza Mountain Estates
Boulder
Coal Creek
Crisman
Eldorado Springs
Glendale
Gold Hill
Gunbarrel
Hidden Lake
Jamestown
Lafayette
Lazy Acres
Leyner
Louisville
Lyons
Mountain Meadows
Nederland
Niwot
Paragon Estates
Pine Brook Hill
Seven Hills
St. Ann Highlands
Sugarloaf
Sunshine
Superior
Tall Timber
Valmont
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 Sep 19, 2026.