Frost Dates for 82520 — Lander, Wyoming

Half of springs at Lander 11 SSE, WY see their last 32°F night by May 13; only one in ten is past it by May 1, and one in ten still has one after June 1. Planting tender crops after May 20 leaves a 30% risk of a frost on them, after May 25 20%, and after June 1 10%. The 19 days between the even-odds date and the one-in-ten date is wider than at 91% of the 33 Wyoming stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 2 in half of years, as early as September 20 one year in ten, and holds off past October 15 one year in ten. A hard freeze of 28°F follows 11 days later, around October 13; in spring the one-in-ten date for 28°F is May 16, 16 days before the 32°F one. The freeze-free season lasts 140 days in a typical year, longer than at 82% of the 33 Wyoming stations; it reaches 159 days one year in ten and falls short of 120 one year in ten. On average 175 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 16 days longer, to about May 29, and return around September 22. Severe cold of 16°F or below comes every winter, usually between November 7 and March 24.

July is the warmest month at Lander 11 SSE, WY, averaging 86°F by day and 56°F at night; January is the coldest at 35°F and 13°F. A freezing night is all but certain in every month from October to May (a 90% chance or more). From July to August the chance of a 32°F night stays under 10% each month. In spring, June still brings one in 12% of years.

Warmth for growing adds up to 2,231 growing degree days a year (base 50°F), more than at 70% of the 33 Wyoming stations. 25% of them (566) have built up by the end of June, and July adds the most, 661. Precipitation totals 16.2 inches a year, most in May (2.8") and least in July (0.8"); May to September bring 43% of it.

The nearest other station, Riverton, WY, 25 miles northeast of Lander and 818 feet lower, has a last frost 1 day earlier (May 12), a first frost 8 days earlier (September 24), a season 8 days shorter.

The first measurable snow (0.1 inch or more) in Lander usually arrives around October 5, and the last of the season around May 11. Those are the middle dates across the winters of 1991–2020 at Lander Hunt Field Airport, WY, 7.6 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 2 days after the last snow.

ZIP 82520 is 4 miles from Lander 11 SSE, WY, which stands at 5,773 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 82520 in zone 5a, the band where the coldest night of the year averaged -20 to -15°F (-28.9 to -26.1°C) over 1991–2020; a zone describes winter lows, not frost dates.