Frost Dates for 82426 — Greybull, Wyoming

Half of springs at Greybull, WY see their last 32°F night by May 11; only one in ten is past it by April 30, and one in ten still has one after May 24. Planting tender crops after May 16 leaves a 30% risk of a frost on them, after May 20 20%, and after May 24 10%. The 13 days between the even-odds date and the one-in-ten date is the narrowest of the 33 Wyoming stations behind this site's ZIP pages.

In fall the first 32°F night comes by September 23 in half of years, as early as September 11 one year in ten, and holds off past October 6 one year in ten. A hard freeze of 28°F follows 10 days later, around October 3; in spring the one-in-ten date for 28°F is May 15, 9 days before the 32°F one. The freeze-free season lasts 133 days in a typical year, longer than at 67% of the 33 Wyoming stations; it reaches 150 days one year in ten and falls short of 115 one year in ten. On average 185 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 12 days longer, to about May 23, and return around September 14. Severe cold of 16°F or below comes every winter, usually between November 1 and March 29.

July is the warmest month at Greybull, WY, averaging 91°F by day and 55°F at night; January is the coldest at 30°F and 2°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 90% of years.

Warmth for growing adds up to 2,432 growing degree days a year (base 50°F), more than at 85% of the 33 Wyoming stations. 31% of them (746) have built up by the end of June, and July adds the most, 710. Precipitation totals 7.3 inches a year, most in May (1.4") and least in March (0.2"); May to September bring 60% of it.

The nearest other station, Lovell, WY, 30 miles northwest of Greybull, has a last frost 2 days earlier (May 9), a first frost 6 days later (September 29), a season 9 days longer.

The first measurable snow (0.1 inch or more) in Greybull usually arrives around November 6, and the last of the season around March 17. Those are the middle dates across the winters of 1991–2020 at Greybull, WY, 1.4 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 55 days after the last snow.

ZIP 82426 is 1 mile from Greybull, WY, which stands at 3,787 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 82426 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.