Frost Dates for 82729 — Sundance, Wyoming

Half of springs at Sundance, WY see their last 32°F night by May 21; only one in ten is past it by May 9, and one in ten still has one after June 5. Planting tender crops after May 27 leaves a 30% risk of a frost on them, after May 30 20%, and after June 5 10%. The 15 days between the even-odds date and the one-in-ten date is narrower than at 48% of the 33 Wyoming stations behind this site's ZIP pages.

In fall the first 32°F night comes by September 25 in half of years, as early as September 7 one year in ten, and holds off past October 8 one year in ten. A hard freeze of 28°F follows 9 days later, around October 4; in spring the one-in-ten date for 28°F is May 23, 13 days before the 32°F one. The freeze-free season lasts 124 days in a typical year, longer than at 52% of the 33 Wyoming stations; it reaches 144 days one year in ten and falls short of 101 one year in ten. On average 179 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 June 1, and return around September 16. Severe cold of 16°F or below comes every winter, usually between October 29 and April 6.

July is the warmest month at Sundance, WY, averaging 82°F by day and 56°F at night; January is the coldest at 33°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 16% of years.

Warmth for growing adds up to 1,959 growing degree days a year (base 50°F), fewer than at 67% of the 33 Wyoming stations. 25% of them (499) have built up by the end of June, and July adds the most, 581. Precipitation totals 20.3 inches a year, most in May (3.5") and least in December (0.5"); May to September bring 59% of it.

The nearest other station, Devils Twr #2, WY, 21 miles northwest of Sundance and 833 feet lower, has a last frost 2 days later (May 23), a first frost 5 days earlier (September 20), a season 6 days shorter.

The first measurable snow (0.1 inch or more) in Sundance usually arrives around October 12, and the last of the season around April 29. Those are the middle dates across the winters of 1991–2020 at Sundance, WY, 3.2 miles away: half of years saw snow earlier, half later. Snow fell in 96% of those winters. The last 32°F night of spring typically comes 22 days after the last snow.

ZIP 82729 is 3 miles from Sundance, WY, which stands at 4,695 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 82729 in zone 4b, the band where the coldest night of the year averaged -25 to -20°F (-31.7 to -28.9°C) over 1991–2020; a zone describes winter lows, not frost dates.