Frost Dates for 99702 — Eielson Afb, Alaska

Half of springs at Eielson Field, AK see their last 32°F night by May 20; only one in ten is past it by May 10, and one in ten still has one after June 3. Planting tender crops after May 25 leaves a 30% risk of a frost on them, after May 29 20%, and after June 3 10%. The 14 days between the even-odds date and the one-in-ten date is wider than at 57% of the 37 Alaska stations behind this site's ZIP pages.

In fall the first 32°F night comes by September 1 in half of years, as early as August 20 one year in ten, and holds off past September 16 one year in ten. A hard freeze of 28°F follows 13 days later, around September 14; in spring the one-in-ten date for 28°F is May 25, 9 days before the 32°F one. The freeze-free season lasts 104 days in a typical year, shorter than at 89% of the 37 Alaska stations; it reaches 121 days one year in ten and falls short of 85 one year in ten. On average 223 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 11 days longer, to about May 31, and return around August 22. Severe cold of 16°F or below comes every winter, usually between October 8 and April 16.

July is the warmest month at Eielson Field, AK, averaging 72°F by day and 50°F at night; January is the coldest at 0°F and -18°F. A freezing night is all but certain in every month from September to May (a 90% chance or more). July is the only month with under a 10% chance of a 32°F night. In spring, June still brings one in 15% of years.

Warmth for growing adds up to 868 growing degree days a year (base 50°F), more than at 84% of the 37 Alaska stations. 38% of them (334) have built up by the end of June, and July adds the most, 340. Precipitation totals 12.9 inches a year, most in July (2.7") and least in March (0.3"); May to September bring 74% of it.

The nearest other station, N Pole 1N, AK, 12 miles northwest of Eielson Afb, has a last frost 2 days later (May 22), a first frost 1 day later (September 2), a season 2 days shorter.

The first measurable snow (0.1 inch or more) in Eielson Afb usually arrives around October 7, and the last of the season around April 15. Those are the middle dates across the winters of 1991–2020 at Eielson Field, AK, 2.4 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 35 days after the last snow.

ZIP 99702 is 2 miles from Eielson Field, AK, which stands at 547 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 99702 in zone 2a, the band where the coldest night of the year averaged -50 to -45°F (-45.6 to -42.8°C) over 1991–2020; a zone describes winter lows, not frost dates.