Frost Dates for 84074 — Tooele, Utah

Half of springs at Tooele, UT see their last 32°F night by May 2; only one in ten is past it by April 16, and one in ten still has one after May 28. Planting tender crops after May 11 leaves a 30% risk of a frost on them, after May 17 20%, and after May 28 10%. The 26 days between the even-odds date and the one-in-ten date is wider than at 95% 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 16 in half of years, as early as October 2 one year in ten, and holds off past November 2 one year in ten. A hard freeze of 28°F follows 11 days later, around October 27; in spring the one-in-ten date for 28°F is May 7, 21 days before the 32°F one. The freeze-free season lasts 165 days in a typical year, longer than at 61% of the 66 Utah stations; it reaches 190 days one year in ten and falls short of 138 one year in ten. On average 128 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 14 days longer, to about May 16, and return around October 6. Severe cold of 16°F or below comes every winter, usually between November 27 and February 20.

July is the warmest month at Tooele, UT, averaging 91°F by day and 64°F at night; December is the coldest at 39°F and 21°F. A freezing night is all but certain in every month from November to April (a 90% chance or more). From June to September the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 52% of years.

Warmth for growing adds up to 3,287 growing degree days a year (base 50°F), more than at 74% of the 66 Utah stations. 30% of them (979) have built up by the end of June, and July adds the most, 860. Precipitation totals 18.6 inches a year, most in May (2.4") and least in August (0.7"); May to September bring 33% of it.

The nearest other station, Grantsville 2W, UT, 12 miles west of Tooele and 394 feet lower, has the same 50% last-frost date, a first frost 2 days earlier (October 14), a season 1 day shorter.

The first measurable snow (0.1 inch or more) in Tooele usually arrives around November 1, and the last of the season around April 18. Those are the middle dates across the winters of 1991–2020 at Tooele, UT, 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 14 days after the last snow.

ZIP 84074 is 2 miles from Tooele, UT, which stands at 4,944 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 84074 in zone 7a, the band where the coldest night of the year averaged 0 to 5°F (-17.8 to -15.0°C) over 1991–2020; a zone describes winter lows, not frost dates.