Frost Dates for 84078 — Vernal, Utah

Half of springs at Vernal, UT see their last 32°F night by May 7; only one in ten is past it by April 24, and one in ten still has one after May 28. Planting tender crops after May 15 leaves a 30% risk of a frost on them, after May 20 20%, and after May 28 10%. The 21 days between the even-odds date and the one-in-ten date is wider than at 74% of the 66 Utah stations behind this site's ZIP pages, so a fixed calendar date is a gamble here.

In fall the first 32°F night comes by October 6 in half of years, as early as September 23 one year in ten, and holds off past October 20 one year in ten. A hard freeze of 28°F follows 12 days later, around October 18; in spring the one-in-ten date for 28°F is May 11, 17 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 170 days one year in ten and falls short of 125 one year in ten. On average 174 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 23, and return around September 27. Severe cold of 16°F or below comes every winter, usually between November 17 and March 8.

July is the warmest month at Vernal, UT, averaging 89°F by day and 57°F at night; January is the coldest at 29°F and 10°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 71% of years.

Warmth for growing adds up to 2,514 growing degree days a year (base 50°F), fewer than at 62% of the 66 Utah stations. 30% of them (761) have built up by the end of June, and July adds the most, 704. Precipitation totals 9.1 inches a year, most in September (1.2") and least in July (0.5"); May to September bring 45% of it.

The nearest other station, Roosevelt Radio, UT, 27 miles southwest of Vernal and 331 feet lower, has a last frost 16 days later (May 23), a first frost 14 days earlier (September 22), a season 29 days shorter.

The first measurable snow (0.1 inch or more) in Vernal usually arrives around November 14, and the last of the season around March 7. Those are the middle dates across the winters of 1991–2020 at Vernal, UT, 5.1 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 61 days after the last snow.

ZIP 84078 is 5 miles from Vernal, UT, which stands at 5,345 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 84078 in zone 5b, the band where the coldest night of the year averaged -15 to -10°F (-26.1 to -23.3°C) over 1991–2020; a zone describes winter lows, not frost dates.