When is the last frost in Denver, CO?

The average (50% probability) last spring frost in Denver is May 5, based on NOAA 1991–2020 normals. A 1-in-10 risk remains until May 19.

When is the first frost in Denver?

The average first fall frost in Denver is October 9, with a growing season of about 156 days.

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Denver, Colorado frost dates

Average last spring frost: May 5. Average first fall frost: October 9. That gives a growing season of about 156 days. For frost-tender plants, a safer planting date is May 19, after which a freeze happens in only 1 year in 10.

Last frost (50%)

May 5

1-in-10 risk after May 19

First frost (50%)

Oct 9

1-in-10 risk before Sep 27

Growing season

156 days

median frost-free days

Hard freeze (28°F)

Apr 25

median last 28°F in spring

Frost risk by date

Chance of frost	Spring: frost after	Fall: frost before
90%	April 23	October 20
70%	April 30	October 14
50%	May 5	October 9
30%	May 11	October 4
10%	May 19	September 27

Read the spring column like this: there is a 10% chance of a 32°F freeze after May 19. These are NOAA probabilities for the Denver International Airport weather station (USW00003017, elevation 1650 m), 1991–2020.

Denver vegetable planting calendar

Dates count from the 50% last-frost date (May 5). For tomatoes, peppers and other frost-tender crops, waiting until the 10% date (May 19) is the cautious choice.

Crop	Start seeds indoors	Plant out
Beans	Apr 14	May 12 (usually sown directly in the garden)
Broccoli	Feb 24	Apr 7
Brussels sprouts	Feb 24	Apr 7
Cabbage	Feb 17	Mar 31
Cauliflower	Mar 10	Apr 21
Sweet corn	Apr 7	May 5 (usually sown directly in the garden)
Cucumbers	Apr 21	May 12
Kale	Feb 17	Mar 31
Leeks	Jan 20	Mar 31
Lettuce	Mar 17	Apr 21
Melons	Apr 28	May 19
Onions	Jan 13	Mar 24 (from seed; sets and transplants go out at the same time)
Peas	Mar 10	Apr 7 (usually sown directly in the garden)
Peppers	Mar 24	May 19
Squash	Apr 28	May 19
Tomatoes	Mar 10	May 5

Offsets from Oregon State University Extension's seed-starting table. "Plant out" means transplant, or sow directly for crops usually grown from seed.

Fall frost and season extension

The first fall freeze usually arrives around October 9. There's a 1-in-10 chance it comes before September 27. Harvest tender crops such as basil, tomatoes, peppers and squash before then, or cover them on cold nights. Cool-season crops like kale, cabbage and Brussels sprouts handle light frost, and often taste sweeter after it. A hard freeze (28°F) typically comes around October 18.

Nearby cities

City	Last frost (50%)	First frost (50%)	Distance
Colorado Springs, CO	May 3	Oct 8	~114 km
Cheyenne, WY	May 12	Oct 1	~147 km
Pueblo, CO	Apr 30	Oct 9	~172 km
Grand Junction, CO	Apr 28	Oct 16	~340 km
Santa Fe, NM	May 4	Oct 15	~484 km
Rapid City, SD	May 12	Oct 1	~487 km

More: all Colorado frost dates