Frost Dates for 82930 — Evanston, Wyoming

Half of springs at Evanston 1 E, WY see their last 32°F night by June 12; only one in ten is past it by May 26, and one in ten still has one after July 2. Planting tender crops after June 20 leaves a 30% risk of a frost on them, after June 24 20%, and after July 2 10%. The 20 days between the even-odds date and the one-in-ten date is wider than at 97% of the 33 Wyoming stations behind this site's ZIP pages.

In fall the first 32°F night comes by September 12 in half of years, as early as August 26 one year in ten, and holds off past September 25 one year in ten. A hard freeze of 28°F follows 12 days later, around September 24; in spring the one-in-ten date for 28°F is June 14, 18 days before the 32°F one. The freeze-free season lasts 90 days in a typical year, shorter than at 82% of the 33 Wyoming stations; it reaches 113 days one year in ten and falls short of 62 one year in ten. On average 210 nights a year drop to 32°F or below. Severe cold of 16°F or below comes every winter, usually between October 31 and April 5.

July is the warmest month at Evanston 1 E, WY, averaging 81°F by day and 48°F at night; January is the coldest at 33°F and 11°F. A freezing night is all but certain in every month from September to May (a 90% chance or more). No month is safe from a 32°F night: even the warmest has at least a 10% chance. In spring, June still brings one in 78% of years and July still brings one in 12% of years.

Warmth for growing adds up to 1,359 growing degree days a year (base 50°F), fewer than at 82% of the 33 Wyoming stations. 23% of them (307) have built up by the end of June, and July adds the most, 446. Precipitation totals 12.1 inches a year, most in May (1.9") and least in February (0.6"); May to September bring 50% of it.

The nearest other station, Mountain View, WY, 30 miles east of Evanston, has a last frost 2 days later (June 14), a first frost 3 days earlier (September 9), a season 6 days shorter.

The first measurable snow (0.1 inch or more) in Evanston usually arrives around October 23, and the last of the season around April 12. Those are the middle dates across the winters of 1991–2020 at Evanston 1 E, WY, 2.3 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 61 days after the last snow.

ZIP 82930 is 2 miles from Evanston 1 E, WY, which stands at 6,825 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 82930 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.