Frost Dates for 85354 — Tonopah, Arizona

Half of springs at Painted Rock Dam, AZ see their last 32°F night by January 21; only one in ten is past it by December 24, and one in ten still has one after February 18. Planting tender crops after February 3 leaves a 30% risk of a frost on them, after February 10 20%, and after February 18 10%. The 28 days between the even-odds date and the one-in-ten date is wider than at 77% of the 99 Arizona 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 December 15 in half of years, as early as November 27 one year in ten, and holds off past January 4 one year in ten. A hard freeze of 28°F follows 13 days later, around December 28; in spring the one-in-ten date for 28°F is February 6, 12 days before the 32°F one. The freeze-free season lasts 327 days in a typical year, longer than at 84% of the 99 Arizona stations; it reaches 357 days one year in ten and falls short of 294 one year in ten. On average 9 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 22 days longer, to about February 12, and return around December 1. A 24°F night is unusual: 11% of winters had one.

July is the warmest month at Painted Rock Dam, AZ, averaging 108°F by day and 82°F at night; December is the coldest at 69°F and 40°F. From March to October the chance of a 32°F night stays under 10% each month. In spring, February still brings one in 33% of years.

Warmth for growing adds up to 8,825 growing degree days a year (base 50°F), more than at 91% of the 103 Arizona stations. 41% of them (3,640) have built up by the end of June, and July adds the most, 1,383. Precipitation totals 6.2 inches a year, most in July (0.9") and least in June (0.0"); May to September bring 39% of it.

The nearest other station, Wittmann 1SE, AZ, 36 miles northeast of Tonopah and 1,115 feet higher, has a last frost 15 days later (February 5), a first frost 4 days earlier (December 11), a season 21 days shorter.

Measurable snow is rare here: only 0 of 17 winters from 1991 to 2020 recorded 0.1 inch or more at Aguila, AZ, 35.3 miles away, so there is no typical first-snow date to plan around.

ZIP 85354 is 26 miles from Painted Rock Dam, AZ, which stands at 568 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. That is farther than 25 miles, so local frost can differ noticeably from these figures. The 2023 USDA Plant Hardiness Zone Map lists ZIP 85354 in zone 9b, the band where the coldest night of the year averaged 25 to 30°F (-3.9 to -1.1°C) over 1991–2020; a zone describes winter lows, not frost dates.