Denver, Colorado: freeze dates & growing season

Three different things get called “Denver” here, so this page is explicit about all three: the metro label (Denver), the anchor geography (Census ZCTA 80202, a downtown ZIP-code area), and the climate record (the NOAA station below). Windows are calculated from the station — not from your street address.

Climate basis: NOAA station Denver Water Dept, CO (USC00052223), 2 mi (3 km) from the ZCTA 80202 centroid, elevation 5228 ft, on the 1991–2020 climate normals.

Last spring freezeApril 301-in-10 after May 13

First fall freezeOctober 121-in-10 before Sep 28

Frost-free season≈ 165 daysmedian at 32°F

Hard freeze, 28°Apr 18 – Oct 21kills even hardy greens

USDA zone6a-10 to -5°F winter low — not frost timing

The year

indoors under lights
in the garden
frost-free season
1-in-10 years still freeze to May 13

The Denver year: hatched areas are the freeze-likely seasons in 1991–2020 normals.

What that means in practice

Tomatoes: plant May 7 – May 21
Peas: plant March 19 – April 2
Garlic: plant cloves October 19 – October 26

All 79 crops in Denver

These windows describe typical years (1991–2020 climate normals), not this year's forecast. Freezes happen outside them — especially in frost pockets, valleys, and urban edges. Watch the forecast before committing tender plants.

Check a specific ZIP instead

Metro climates vary — elevation, water, and urban heat shift freeze dates by days to weeks. Look up your exact ZIP:

Nearby reviewed metros

Colorado Springs, CO · Cheyenne, WY · Albuquerque, NM · Salt Lake City, UT · Wichita, KS