Frost Dates for 85138 — Maricopa, Arizona

Half of springs at Maricopa 4 N, AZ see their last 32°F night by February 23; only one in ten is past it by January 29, and one in ten still has one after March 15. Planting tender crops after March 3 leaves a 30% risk of a frost on them, after March 8 20%, and after March 15 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 November 24 in half of years, as early as November 10 one year in ten, and holds off past December 8 one year in ten. A hard freeze of 28°F follows 12 days later, around December 6; in spring the one-in-ten date for 28°F is February 28, 15 days before the 32°F one. The freeze-free season lasts 274 days in a typical year, longer than at 61% of the 98 Arizona stations; it reaches 304 days one year in ten and falls short of 245 one year in ten. On average 32 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 March 12, and return around November 14. Nights of 24°F, cold enough to damage hardier plants, come in 85% of winters and 16°F in 4%.

July is the warmest month at Maricopa 4 N, AZ, averaging 109°F by day and 78°F at night; December is the coldest at 68°F and 35°F. A freezing night is all but certain in every month from December to January (a 90% chance or more). From April to October the chance of a 32°F night stays under 10% each month. In spring, February still brings one in 79% of years and March still brings one in 34% of years.

Warmth for growing adds up to 8,135 growing degree days a year (base 50°F), more than at 79% of the 102 Arizona stations. 40% of them (3,292) have built up by the end of June, and July adds the most, 1,344. Precipitation totals 7.2 inches a year, most in August (1.0") and least in June (0.1"); May to September bring 38% of it.

The nearest other station, Casa Grande, AZ, 17 miles southeast of Maricopa and 240 feet higher, has a last frost 18 days earlier (February 5), a first frost 12 days later (December 6), a season 31 days longer.

Measurable snow is rare here: only 0 of 21 winters from 1991 to 2020 recorded 0.1 inch or more at Maricopa 4 N, AZ, 8 miles away, so there is no typical first-snow date to plan around.

ZIP 85138 is 8 miles from Maricopa 4 N, AZ, which stands at 1,160 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 85138 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.