Frost Dates in Arizona

At the middle station of the 86 in Arizona where a freeze comes every year, the last spring frost (50%) is April 1 and the first fall frost November 11, a freeze-free season of 223 days. The last frost is earliest at Peoria (Youngtown, AZ, January 20) and latest at Grand Canyon (Grand Canyon Np Airport, AZ, June 17), 148 days apart. The season runs from 97 days at Grand Canyon to 332 at Tucson.

At 4 of the 102 stations a 32°F night comes in fewer than half of winters. Where a freeze does come, it is rarest at San Luis (8% of winters), Phoenix (18% of winters) and Mohave Valley (37% of winters).

56 of these stations were also in NOAA's previous normals, for 1981–2010. Between the two, the median station's freeze-free season grew 3 days longer, with the last spring frost 3 days earlier and the first fall frost 1 day later; the season lengthened at 33 stations and shortened at 19. The two periods share twenty years, so the change reflects mostly 2011–2020 against 1981–1990.