Frost Dates for 85550 — San Carlos, Arizona

Half of springs at Black Rvr Pumps, AZ see their last 32°F night by May 16; only one in ten is past it by May 2, and one in ten still has one after June 2. Planting tender crops after May 23 leaves a 30% risk of a frost on them, after May 28 20%, and after June 2 10%. The 17 days between the even-odds date and the one-in-ten date is narrower than at 80% of the 98 Arizona stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 13 in half of years, as early as September 30 one year in ten, and holds off past October 27 one year in ten. A hard freeze of 28°F follows 10 days later, around October 23; in spring the one-in-ten date for 28°F is May 20, 13 days before the 32°F one. The freeze-free season lasts 149 days in a typical year, shorter than at 88% of the 98 Arizona stations; it reaches 169 days one year in ten and falls short of 129 one year in ten. On average 159 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 13 days longer, to about May 29, and return around October 4. Severe cold of 16°F or below comes every winter, usually between November 23 and March 7.

July is the warmest month at Black Rvr Pumps, AZ, averaging 89°F by day and 55°F at night; January is the coldest at 52°F and 20°F. A freezing night is all but certain in every month from October to May (a 90% chance or more). From July to August the chance of a 32°F night stays under 10% each month. In spring, June still brings one in 13% of years.

Warmth for growing adds up to 2,842 growing degree days a year (base 50°F), fewer than at 88% of the 102 Arizona stations. 31% of them (885) have built up by the end of June, and July adds the most, 680. Precipitation totals 18.6 inches a year, most in July (3.3") and least in April (0.5"); May to September bring 52% of it.

The nearest other station, Fort Thomas 2 SW, AZ, 26 miles south of San Carlos and 3,230 feet lower, has a last frost 45 days earlier (April 1), a first frost 24 days later (November 6), a season 68 days longer.

The first measurable snow (0.1 inch or more) in San Carlos usually arrives around January 2, and the last of the season around February 28. Those are the middle dates across the winters of 1991–2020 at Black Rvr Pumps, AZ, 22.3 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 77 days after the last snow.

ZIP 85550 is 22 miles from Black Rvr Pumps, AZ, which stands at 6,065 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 85550 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.