Frost dates / Colorado / Windsor

Frost dates in Windsor, CO

The station on this page is FT COLLINS 4 E, CO US (USC00053006), 8.8 miles from the city point. Population in the Census 2024 estimate is 41,734.

Zone 5bUSDA average annual extreme minimum -15°F to -10°F, from ZIP 80550 (1.1 miles from the city point used on this page).

Median last 32°F is May 3. Median first 32°F is October 6. The 50% growing-season length is 154 days. The green band runs from the median last frost to the median first frost. Thin ticks mark the 10%, 50%, and 90% dates.

Outside the median season Growing seasonTicks: 10%, 50%, and 90%

Last 32°F in spring

NCEI’s probability is the chance the last spring minimum of 32°F or lower occurs on or after the date.

Probability	Date	How to read it
90%	April 21	Earlier date. A last 32°F on or after this day is common.
50%	May 3	Median.
10%	May 15	Later date. A last 32°F on or after this day is uncommon.

First 32°F in fall

NCEI’s probability is the chance the first autumn minimum of 32°F or lower occurs on or before the date.

Probability	Date	How to read it
10%	September 22	Earlier date. A first 32°F on or before this day is uncommon.
50%	October 6	Median.
90%	October 17	Later date. A first 32°F on or before this day is common.

32°F growing-season length

Days between the last spring 32°F and the first autumn 32°F. The figure is a length the season meets or exceeds at that probability, from NCEI, not a subtraction done on this site.

Probability the season is at least this long	Days
10%	171
50%	154
90%	135

28°F threshold

	10%	50%	90%
Last, on or after	May 8	April 23	April 8
First, on or before	September 30	October 14	October 26
Season at least	192 days	174 days	153 days

36°F threshold

	10%	50%	90%
Last, on or after	May 26	May 14	May 3
First, on or before	September 13	September 27	October 8
Season at least	151 days	136 days	118 days

Station FT COLLINS 4 E, CO US (USC00053006). Completeness flag S, 29 years used for the 32°F dates. NCEI’s annual probability of at least one day at or below 32°F is 100%. Freeze dates are conditional on that threshold occurring. Elevation 1499.6 m. The same probability language applies to the 28°F and 36°F rows when those dates passed the same quality checks.

Check a crop against this station

Windsor, CO

Zone 5bAverage annual extreme minimum -15°F to -10°F

Outside the median season Growing seasonTicks: 10%, 50%, and 90%

Colorado. Nearest qualified station: FT COLLINS 4 E, CO US (USC00053006), 8.8 miles. Median last 32°F May 3. Median first 32°F October 6. The 50% growing-season length is 154 days.

Open the ZIP page

32°F probabilities at this station

	10%	50%	90%
Last 32°F on or after	May 15	May 3	April 21
First 32°F on or before	September 22	October 6	October 17

Column order matches the NCEI file: for the last freeze, 10% is the later date and 90% is the earlier date. How to read the probabilities.

A wall calendar surrounded by vegetables, herbs, seed packets, and watering cans.

Planting calendar

Frost dates for Colorado are above. Planting windows appear for states with a cited extension guide. The fall and seed tools use the numbers you enter and the station dates.

Date checks use your device’s calendar and appear after the page loads.