Frost Dates for 86011 — Flagstaff, Arizona

Half of springs at Williams 35 NNW, AZ see their last 32°F night by May 9; only one in ten is past it by April 24, and one in ten still has one after May 27. Planting tender crops after May 15 leaves a 30% risk of a frost on them, after May 21 20%, and after May 27 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 October 19 in half of years, as early as October 3 one year in ten, and holds off past November 3 one year in ten. A hard freeze of 28°F follows 12 days later, around October 31; in spring the one-in-ten date for 28°F is May 14, 13 days before the 32°F one. The freeze-free season lasts 161 days in a typical year, shorter than at 84% of the 98 Arizona stations; it reaches 183 days one year in ten and falls short of 137 one year in ten. On average 144 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 15 days longer, to about May 24, and return around October 6. Severe cold of 16°F or below comes every winter, usually between November 29 and February 24.

July is the warmest month at Williams 35 NNW, AZ, averaging 88°F by day and 57°F at night; December is the coldest at 44°F and 22°F. A freezing night is all but certain in every month from November to April (a 90% chance or more). From June to September the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 74% of years.

Warmth for growing adds up to 2,748 growing degree days a year (base 50°F), fewer than at 90% of the 102 Arizona stations. 30% of them (834) have built up by the end of June, and July adds the most, 694. Precipitation totals 12.1 inches a year, most in July (2.0") and least in June (0.3"); May to September bring 50% of it.

The nearest other station, Grand Canyon Np Airport, AZ, 23 miles north of Flagstaff and 616 feet higher, has a last frost 39 days later (June 17), a first frost 25 days earlier (September 24), a season 64 days shorter.

The first measurable snow (0.1 inch or more) in Flagstaff usually arrives around November 21, and the last of the season around April 2. Those are the middle dates across the winters of 1991–2020 at Williams, AZ, 28 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes 37 days after the last snow.

ZIP 86011 is 18 miles from Williams 35 NNW, AZ, which stands at 5,990 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. ZIP 86011 is not in the ZIP-code listing of the 2023 USDA Plant Hardiness Zone Map, so no zone is given.