Frost Dates for 85634 — Sells, Arizona

Half of springs at Kitt Peak, AZ see their last 32°F night by April 26; only one in ten is past it by April 1, and one in ten still has one after May 17. Planting tender crops after May 4 leaves a 30% risk of a frost on them, after May 9 20%, and after May 17 10%. The 21 days between the even-odds date and the one-in-ten date is narrower than at 47% of the 98 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 November 4 in half of years, as early as October 18 one year in ten, and holds off past November 24 one year in ten. A hard freeze of 28°F follows 13 days later, around November 17; in spring the one-in-ten date for 28°F is May 5, 12 days before the 32°F one. The freeze-free season lasts 195 days in a typical year, shorter than at 70% of the 98 Arizona stations; it reaches 225 days one year in ten and falls short of 165 one year in ten. On average 59 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 11 days longer, to about May 7, and return around October 26. Nights of 24°F, cold enough to damage hardier plants, come in 100% of winters and 16°F in 69%.

July is the warmest month at Kitt Peak, AZ, averaging 80°F by day and 61°F at night; December is the coldest at 50°F and 34°F. A freezing night is all but certain in every month from November to March (a 90% chance or more). From June to September the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 85% of years and May still brings one in 37% of years.

Warmth for growing adds up to 3,241 growing degree days a year (base 50°F), fewer than at 83% of the 102 Arizona stations. 35% of them (1,138) have built up by the end of June, and July adds the most, 634. Precipitation totals 20.0 inches a year, most in August (4.4") and least in April (0.3"); May to September bring 58% of it.

The nearest other station, Anvil Rch, AZ, 32 miles east of Sells and 4,031 feet lower, has a last frost 30 days earlier (March 27), a first frost 5 days later (November 9), a season 31 days longer.

The first measurable snow (0.1 inch or more) in Sells usually arrives around December 20, and the last of the season around March 9. Those are the middle dates across the winters of 1991–2020 at Kitt Peak, AZ, 20.1 miles away: half of years saw snow earlier, half later. Snow fell in 93% of those winters. The last 32°F night of spring typically comes 48 days after the last snow.

ZIP 85634 is 20 miles from Kitt Peak, AZ, which stands at 6,790 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 85634 in zone 9a, the band where the coldest night of the year averaged 20 to 25°F (-6.7 to -3.9°C) over 1991–2020; a zone describes winter lows, not frost dates.