Frost Dates for 80122 — Littleton, Colorado

Half of springs at Denver Centennial Airport, CO see their last 32°F night by May 5; only one in ten is past it by April 24, and one in ten still has one after May 17. Planting tender crops after May 10 leaves a 30% risk of a frost on them, after May 13 20%, and after May 17 10%. The 12 days between the even-odds date and the one-in-ten date is narrower than at 81% of the 110 Colorado stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 8 in half of years, as early as September 25 one year in ten, and holds off past October 20 one year in ten. A hard freeze of 28°F follows 9 days later, around October 17; in spring the one-in-ten date for 28°F is May 9, 8 days before the 32°F one. The freeze-free season lasts 154 days in a typical year, longer than at 68% of the 110 Colorado stations; it reaches 170 days one year in ten and falls short of 135 one year in ten. On average 155 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 10 days longer, to about May 15, and return around October 1. Severe cold of 16°F or below comes every winter, usually between November 13 and March 20.

July is the warmest month at Denver Centennial Airport, CO, averaging 87°F by day and 59°F at night; December is the coldest at 44°F and 19°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 69% of years.

Warmth for growing adds up to 2,708 growing degree days a year (base 50°F), more than at 58% of the 110 Colorado stations. 30% of them (817) have built up by the end of June, and July adds the most, 711. Precipitation totals 15.0 inches a year, most in August (2.3") and least in January (0.4"); May to September bring 63% of it.

The nearest other station, Marston Fltr Plt, CO, 6 miles northwest of Littleton and 273 feet lower, has a last frost 3 days earlier (May 2), a first frost 3 days later (October 11), a season 6 days longer.

The first measurable snow (0.1 inch or more) in Littleton usually arrives around October 20, and the last of the season around May 2. Those are the middle dates across the winters of 1991–2020 at Denver 9.4 S, CO, 1.7 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 3 days after the last snow.

ZIP 80122 is 6 miles from Denver Centennial Airport, CO, which stands at 5,883 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 4 other ZIP codes share the station; its figures are presented in full for 80126 (Highlands Ranch). The 2023 USDA Plant Hardiness Zone Map lists ZIP 80122 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.