Frost Dates for 84021 — Duchesne, Utah

Half of springs at Duchesne, UT see their last 32°F night by May 6; only one in ten is past it by April 22, and one in ten still has one after May 26. Planting tender crops after May 13 leaves a 30% risk of a frost on them, after May 18 20%, and after May 26 10%. The 20 days between the even-odds date and the one-in-ten date is wider than at 61% of the 66 Utah stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 5 in half of years, as early as September 24 one year in ten, and holds off past October 18 one year in ten. A hard freeze of 28°F follows 11 days later, around October 16; in spring the one-in-ten date for 28°F is May 7, 19 days before the 32°F one. The freeze-free season lasts 150 days in a typical year, shorter than at 53% of the 66 Utah stations; it reaches 169 days one year in ten and falls short of 127 one year in ten. On average 171 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 22, and return around September 26. Severe cold of 16°F or below comes every winter, usually between November 14 and March 8.

July is the warmest month at Duchesne, UT, averaging 89°F by day and 56°F at night; January is the coldest at 33°F and 11°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 68% of years.

Warmth for growing adds up to 2,560 growing degree days a year (base 50°F), fewer than at 59% of the 66 Utah stations. 32% of them (807) have built up by the end of June, and July adds the most, 694. Precipitation totals 9.4 inches a year, most in August (1.4") and least in January (0.5"); May to September bring 54% of it.

The nearest other station, Roosevelt Radio, UT, 28 miles east of Duchesne and 537 feet lower, has a last frost 17 days later (May 23), a first frost 13 days earlier (September 22), a season 29 days shorter.

The first measurable snow (0.1 inch or more) in Duchesne usually arrives around November 13, and the last of the season around April 4. Those are the middle dates across the winters of 1991–2020 at Duchesne, UT, 3.3 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 32 days after the last snow.

ZIP 84021 is 3 miles from Duchesne, UT, which stands at 5,551 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 84021 in zone 6a, the band where the coldest night of the year averaged -10 to -5°F (-23.3 to -20.6°C) over 1991–2020; a zone describes winter lows, not frost dates.