Frost Dates for 85648 — Rio Rico, Arizona

Half of springs at Nogales 6 N, AZ see their last 32°F night by April 16; only one in ten is past it by March 28, and one in ten still has one after May 4. Planting tender crops after April 24 leaves a 30% risk of a frost on them, after April 29 20%, and after May 4 10%. The 18 days between the even-odds date and the one-in-ten date is narrower than at 74% of the 98 Arizona stations behind this site's ZIP pages.

In fall the first 32°F night comes by November 2 in half of years, as early as October 19 one year in ten, and holds off past November 16 one year in ten. A hard freeze of 28°F follows 12 days later, around November 14; in spring the one-in-ten date for 28°F is April 15, 19 days before the 32°F one. The freeze-free season lasts 199 days in a typical year, shorter than at 68% of the 98 Arizona stations; it reaches 222 days one year in ten and falls short of 175 one year in ten. On average 92 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 16 days longer, to about May 2, and return around October 24. Nights of 24°F, cold enough to damage hardier plants, come in 100% of winters and 16°F in 65%.

July is the warmest month at Nogales 6 N, AZ, averaging 94°F by day and 65°F at night; December is the coldest at 65°F and 28°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 82% of years and May still brings one in 16% of years.

Warmth for growing adds up to 4,976 growing degree days a year (base 50°F), fewer than at 61% of the 102 Arizona stations. 37% of them (1,837) have built up by the end of June, and July adds the most, 925. Precipitation totals 16.2 inches a year, most in August (3.9") and least in May (0.2"); May to September bring 65% of it.

The nearest other station, Nogales International Airport, AZ, 10 miles southeast of Rio Rico and 471 feet higher, has a last frost 27 days earlier (March 20), a first frost 15 days later (November 17), a season 40 days longer.

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, 2.6 miles away, so there is no typical first-snow date to plan around.

ZIP 85648 is 3 miles from Nogales 6 N, AZ, which stands at 3,461 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 85648 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.