Frost dates / Colorado / Denver

Frost dates in Denver, CO

The station on this page is DENVER-STAPLETON, CO US (USW00023062), 0.6 miles from the city point. Population in the Census 2024 estimate is 729,019.

Zone 6aUSDA average annual extreme minimum -10°F to -5°F, from ZIP 80238 (1.1 miles from the city point used on this page).

Median last 32°F is May 4. Median first 32°F is October 8. The 50% growing-season length is 156 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 20	Earlier date. A last 32°F on or after this day is common.
50%	May 4	Median.
10%	May 16	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 25	Earlier date. A first 32°F on or before this day is uncommon.
50%	October 8	Median.
90%	October 20	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%	175
50%	156
90%	138

28°F threshold

	10%	50%	90%
Last, on or after	May 7	April 22	April 6
First, on or before	October 3	October 18	October 31
Season at least	198 days	177 days	158 days

36°F threshold

	10%	50%	90%
Last, on or after	May 26	May 12	May 2
First, on or before	September 16	October 1	October 13
Season at least	156 days	140 days	121 days

Station DENVER-STAPLETON, CO US (USW00023062). Completeness flag S, 28 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 1611.2 m. The same probability language applies to the 28°F and 36°F rows when those dates passed the same quality checks.

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Denver, CO

Zone 6aAverage annual extreme minimum -10°F to -5°F

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

Colorado. Nearest qualified station: DENVER-STAPLETON, CO US (USW00023062), 0.6 miles. Median last 32°F May 4. Median first 32°F October 8. The 50% growing-season length is 156 days.

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32°F probabilities at this station

	10%	50%	90%
Last 32°F on or after	May 16	May 4	April 20
First 32°F on or before	September 25	October 8	October 20

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.

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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.

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