Frost Dates for 80125 — Littleton, Colorado

Half of springs at Kassler, CO see their last 32°F night by May 8; only one in ten is past it by April 27, and one in ten still has one after May 22. Planting tender crops after May 15 leaves a 30% risk of a frost on them, after May 18 20%, and after May 22 10%. The 14 days between the even-odds date and the one-in-ten date is narrower than at 45% of the 110 Colorado stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 3 in half of years, as early as September 21 one year in ten, and holds off past October 17 one year in ten. A hard freeze of 28°F follows 10 days later, around October 13; in spring the one-in-ten date for 28°F is May 13, 9 days before the 32°F one. The freeze-free season lasts 147 days in a typical year, longer than at 55% of the 110 Colorado stations; it reaches 165 days one year in ten and falls short of 126 one year in ten. On average 156 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 11 days longer, to about May 19, and return around September 27. Severe cold of 16°F or below comes every winter, usually between November 9 and March 27.

July is the warmest month at Kassler, CO, averaging 87°F by day and 59°F at night; December is the coldest at 46°F and 17°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 77% of years.

Warmth for growing adds up to 2,743 growing degree days a year (base 50°F), more than at 63% of the 110 Colorado stations. 30% of them (828) have built up by the end of June, and July adds the most, 705. Precipitation totals 18.2 inches a year, most in May (2.5") and least in January (0.6"); May to September bring 53% of it.

The nearest other station, Roxborough Sp, CO, 4 miles south of Littleton and 530 feet higher, has a last frost 8 days later (May 16), a first frost 2 days earlier (October 1), a season 11 days shorter.

The first measurable snow (0.1 inch or more) in Littleton usually arrives around October 26, and the last of the season around April 28. Those are the middle dates across the winters of 1991–2020 at Kassler, 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 10 days after the last snow.

ZIP 80125 is 2 miles from Kassler, CO, which stands at 5,587 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station; its figures are presented in full for 80129 (Highlands Ranch). The 2023 USDA Plant Hardiness Zone Map lists ZIP 80125 in zone 5b, the band where the coldest night of the year averaged -15 to -10°F (-26.1 to -23.3°C) over 1991–2020; a zone describes winter lows, not frost dates.