Frost Dates for 85621 — Nogales, Arizona

Half of springs at Nogales International Airport, AZ see their last 32°F night by March 20; only one in ten is past it by February 24, and one in ten still has one after April 13. Planting tender crops after March 31 leaves a 30% risk of a frost on them, after April 6 20%, and after April 13 10%. The 24 days between the even-odds date and the one-in-ten date is wider than at 58% 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 17 in half of years, as early as October 30 one year in ten, and holds off past December 3 one year in ten. A hard freeze of 28°F follows 13 days later, around November 30; in spring the one-in-ten date for 28°F is March 21, 23 days before the 32°F one. The freeze-free season lasts 239 days in a typical year, longer than at 53% of the 98 Arizona stations; it reaches 272 days one year in ten and falls short of 208 one year in ten. On average 45 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 24 days longer, to about April 13, and return around November 5. Nights of 24°F, cold enough to damage hardier plants, come in 96% of winters and 16°F in 12%.

July is the warmest month at Nogales International Airport, AZ, averaging 94°F by day and 67°F at night; December is the coldest at 65°F and 34°F. A freezing night is all but certain in every month from December to February (a 90% chance or more). From May to September the chance of a 32°F night stays under 10% each month. In spring, March still brings one in 77% of years and April still brings one in 30% of years.

Warmth for growing adds up to 5,666 growing degree days a year (base 50°F), fewer than at 51% of the 102 Arizona stations. 40% of them (2,270) have built up by the end of June, and July adds the most, 946. Precipitation totals 14.6 inches a year, most in July (4.2") and least in May (0.2"); May to September bring 67% of it.

The nearest other station, Nogales 6 N, AZ, 6 miles northwest of Nogales and 471 feet lower, has a last frost 27 days later (April 16), a first frost 15 days earlier (November 2), a season 40 days shorter.

Measurable snow is rare here: only 3 of 19 winters from 1991 to 2020 recorded 0.1 inch or more at Nogales 6 N, AZ, 5.9 miles away, so there is no typical first-snow date to plan around.

ZIP 85621 is 6 miles from Nogales International Airport, AZ, which stands at 3,932 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 85621 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.