Frost Dates for 82701 — Newcastle, Wyoming

Half of springs at Newcastle, WY see their last 32°F night by May 13; only one in ten is past it by April 30, and one in ten still has one after May 26. Planting tender crops after May 18 leaves a 30% risk of a frost on them, after May 21 20%, and after May 26 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 October 3 in half of years, as early as September 17 one year in ten, and holds off past October 16 one year in ten. A hard freeze of 28°F follows 8 days later, around October 11; in spring the one-in-ten date for 28°F is May 17, 9 days before the 32°F one. The freeze-free season lasts 143 days in a typical year, longer than at 91% of the 33 Wyoming stations; it reaches 161 days one year in ten and falls short of 123 one year in ten. On average 168 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 10 days longer, to about May 23, and return around September 24. Severe cold of 16°F or below comes every winter, usually between November 4 and March 29.

July is the warmest month at Newcastle, WY, averaging 87°F by day and 60°F at night; January is the coldest at 35°F and 14°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 87% of years.

Warmth for growing adds up to 2,641 growing degree days a year (base 50°F), more than at 97% of the 33 Wyoming stations. 28% of them (746) have built up by the end of June, and July adds the most, 725. Precipitation totals 17.1 inches a year, most in May (2.9") and least in January (0.5"); May to September bring 65% of it.

The first measurable snow (0.1 inch or more) in Newcastle usually arrives around November 1, and the last of the season around April 19. Those are the middle dates across the winters of 1991–2020 at Newcastle, WY, 14.9 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 24 days after the last snow.

ZIP 82701 is 15 miles from Newcastle, WY, which stands at 4,415 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 82701 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.