Frost Dates for 85530 — Bylas, Arizona

Half of springs at Fort Thomas 2 SW, AZ see their last 32°F night by April 1; only one in ten is past it by March 15, and one in ten still has one after April 18. Planting tender crops after April 7 leaves a 30% risk of a frost on them, after April 11 20%, and after April 18 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 November 6 in half of years, as early as October 21 one year in ten, and holds off past November 19 one year in ten. A hard freeze of 28°F follows 10 days later, around November 16; in spring the one-in-ten date for 28°F is April 3, 15 days before the 32°F one. The freeze-free season lasts 217 days in a typical year, shorter than at 60% of the 98 Arizona stations; it reaches 240 days one year in ten and falls short of 195 one year in ten. On average 82 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 April 17, and return around October 29. Nights of 24°F, cold enough to damage hardier plants, come in 100% of winters and 16°F in 78%.

July is the warmest month at Fort Thomas 2 SW, AZ, averaging 100°F by day and 71°F at night; December is the coldest at 60°F and 28°F. A freezing night is all but certain in every month from November to March (a 90% chance or more). From May to September the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 50% of years.

Warmth for growing adds up to 5,841 growing degree days a year (base 50°F), more than at 50% of the 102 Arizona stations. 38% of them (2,247) have built up by the end of June, and July adds the most, 1,094. Precipitation totals 10.3 inches a year, most in August (1.9") and least in June (0.2"); May to September bring 51% of it.

The nearest other station, San Carlos Reservoir, AZ, 19 miles northwest of Bylas and 303 feet lower, has a last frost 19 days earlier (March 13), a first frost 13 days later (November 19), a season 30 days longer.

Measurable snow is rare here: only 0 of 15 winters from 1991 to 2020 recorded 0.1 inch or more at San Carlos Reservoir, AZ, 19.3 miles away, so there is no typical first-snow date to plan around.

ZIP 85530 is 14 miles from Fort Thomas 2 SW, AZ, which stands at 2,835 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station; its figures are presented in full for 85543 (Pima). The 2023 USDA Plant Hardiness Zone Map lists ZIP 85530 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.