Frost Dates for 80209 — Denver, Colorado

Half of springs at Denver Water Dept, CO see their last 32°F night by April 30; only one in ten is past it by April 15, and one in ten still has one after May 13. Planting tender crops after May 4 leaves a 30% risk of a frost on them, after May 8 20%, and after May 13 10%. The 13 days between the even-odds date and the one-in-ten date is narrower than at 67% of the 110 Colorado stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 12 in half of years, as early as September 28 one year in ten, and holds off past October 26 one year in ten. A hard freeze of 28°F follows 9 days later, around October 21; in spring the one-in-ten date for 28°F is May 5, 8 days before the 32°F one. The freeze-free season lasts 165 days in a typical year, longer than at 91% of the 110 Colorado stations; it reaches 184 days one year in ten and falls short of 145 one year in ten. On average 150 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 8 days longer, to about May 8, and return around October 4. Severe cold of 16°F or below comes every winter, usually between November 19 and March 10.

July is the warmest month at Denver Water Dept, CO, averaging 91°F by day and 62°F at night; December is the coldest at 47°F and 21°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). From June to August the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 48% of years.

Warmth for growing adds up to 3,396 growing degree days a year (base 50°F), more than at 89% of the 110 Colorado stations. 33% of them (1,109) have built up by the end of June, and July adds the most, 824. Precipitation totals 15.9 inches a year, most in May (2.7") and least in January (0.4"); May to September bring 58% of it.

The nearest other station, Denver-Stapleton, CO, 7 miles northeast of Denver, has a last frost 4 days later (May 4), a first frost 4 days earlier (October 8), a season 9 days shorter.

The first measurable snow (0.1 inch or more) in Denver usually arrives around October 29, and the last of the season around April 30. Those are the middle dates across the winters of 1991–2020 at Denver Water Dept, CO, 2.7 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes on the day of the last snow.

ZIP 80209 is 3 miles from Denver Water Dept, CO, which stands at 5,228 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 14 other ZIP codes share the station; its figures are presented in full for 80219 (Denver). The 2023 USDA Plant Hardiness Zone Map lists ZIP 80209 in zone 6a, the band where the coldest night of the year averaged -10 to -5°F (-23.3 to -20.6°C) over 1991–2020; a zone describes winter lows, not frost dates.