Frost Dates for 85643 — Willcox, Arizona

Half of springs at Willcox, AZ see their last 32°F night by April 9; only one in ten is past it by March 20, and one in ten still has one after April 29. Planting tender crops after April 16 leaves a 30% risk of a frost on them, after April 21 20%, and after April 29 10%. The 20 days between the even-odds date and the one-in-ten date is narrower than at 52% of the 98 Arizona stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 31 in half of years, as early as October 20 one year in ten, and holds off past November 14 one year in ten. A hard freeze of 28°F follows 12 days later, around November 12; in spring the one-in-ten date for 28°F is April 10, 19 days before the 32°F one. The freeze-free season lasts 204 days in a typical year, shorter than at 65% of the 98 Arizona stations; it reaches 225 days one year in ten and falls short of 181 one year in ten. On average 93 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 17 days longer, to about April 26, and return around October 22. Nights of 24°F, cold enough to damage hardier plants, come in 100% of winters and 16°F in 72%.

July is the warmest month at Willcox, AZ, averaging 96°F by day and 66°F at night; December is the coldest at 60°F and 28°F. A freezing night is all but certain in every month from November to March (a 90% chance or more). From May to September the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 68% of years.

Warmth for growing adds up to 5,044 growing degree days a year (base 50°F), fewer than at 60% of the 102 Arizona stations. 38% of them (1,923) have built up by the end of June, and July adds the most, 955. Precipitation totals 12.4 inches a year, most in July (2.6") and least in April (0.2"); May to September bring 57% of it.

The nearest other station, Safford Ag Ctr, AZ, 34 miles north of Willcox and 1,216 feet lower, has a last frost 15 days earlier (March 25), a first frost 9 days later (November 9), a season 24 days longer.

The first measurable snow (0.1 inch or more) in Willcox usually arrives around December 24, and the last of the season around February 1. Those are the middle dates across the winters of 1991–2020 at Willcox, AZ, 7.5 miles away: half of years saw snow earlier, half later. Snow fell in 76% of those winters. The last 32°F night of spring typically comes 67 days after the last snow.

ZIP 85643 is 8 miles from Willcox, AZ, which stands at 4,170 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 85643 in zone 8b, the band where the coldest night of the year averaged 15 to 20°F (-9.4 to -6.7°C) over 1991–2020; a zone describes winter lows, not frost dates.