Frost dates in Fort Collins, Colorado

NOAA 1991–2020 normals for a 32 °F freeze. Low spots and the edge of town run colder than downtown.

Short answer

The average last spring frost in Fort Collins is May 2, and the average first fall frost is October 7, from NOAA's Ft Collins station, 2 miles from the middle of Fort Collins. 1 year in 10 the last frost comes after May 14, and the first one by September 24. That leaves about 158 frost-free days. Fort Collins is in USDA planting zone 5b.

Weather stations around Fort Collins

The first row is the date most people in Fort Collins go by. The others show how far the dates move across the area.

Station	Last spring frost	First fall frost	Frost-free
Ft Collins 2 mi away, 5,004 ft	May 2 1 in 10 after May 14	October 7 1 in 10 by September 24	158 days
Ft Collins 4 E 3 mi away, 4,920 ft	May 3 1 in 10 after May 15	October 6 1 in 10 by September 22	156 days
Loveland 2N 8 mi away, 5,080 ft	May 10 1 in 10 after May 22	October 1 1 in 10 by September 15	144 days
Waterdale 11 mi away, 5,230 ft	May 12 1 in 10 after May 30	October 1 1 in 10 by September 18	142 days
Buckhorn Mtn 1 E 13 mi away, 7,400 ft	May 21 1 in 10 after June 4	September 29 1 in 10 by September 12	131 days

Distances are from the middle of Fort Collins as the Census Bureau maps it. The average date is NOAA's 50% date: half of years have a later last frost, or an earlier first one. Plan by the 1-in-10 date if a freeze would cost you plants. The planting zone is the USDA 2023 zone for ZIP code 80525, at the middle of the city.

Your exact ZIP code

Fort Collins covers a lot of ground. For the station nearest your own street, and its planting zone, type your ZIP code.

How these dates work

Frost dates come from NOAA's 1991 to 2020 Climate Normals, which work out from each weather station's daily lows how likely the last spring freeze and the first fall freeze (32 °F) are by each date. We use the station nearest the middle of your ZIP code and show its height and distance, since a station on a hill or by a lake can differ from your yard.

The average date is the 50% date: half of years have a freeze after the spring date or before the fall one. The 1-in-10 dates are NOAA's 10% dates, the ones to plan by if a late freeze would cost you plants. Within one yard, cold air pools in low spots while walls and paving hold heat, so some corners freeze before others.

More frost dates

All of Colorado, station by station.

Other Colorado cities: Denver · Colorado Springs · Aurora · Lakewood · Thornton