Frost Dates for 99516 — Anchorage, Alaska

Half of springs at Anchorage Rabbit Creek #2, AK see their last 32°F night by May 12; only one in ten is past it by April 30, and one in ten still has one after May 24. Planting tender crops after May 17 leaves a 30% risk of a frost on them, after May 20 20%, and after May 24 10%. The 12 days between the even-odds date and the one-in-ten date is narrower than at 65% of the 37 Alaska stations behind this site's ZIP pages.

In fall the first 32°F night comes by September 26 in half of years, as early as September 12 one year in ten, and holds off past October 9 one year in ten. A hard freeze of 28°F follows 10 days later, around October 6; in spring the one-in-ten date for 28°F is May 10, 14 days before the 32°F one. The freeze-free season lasts 137 days in a typical year, longer than at 51% of the 37 Alaska stations; it reaches 154 days one year in ten and falls short of 117 one year in ten. On average 197 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 27, and return around September 15. Severe cold of 16°F or below comes every winter, usually between October 30 and April 3.

July is the warmest month at Anchorage Rabbit Creek #2, AK, averaging 65°F by day and 49°F at night; January is the coldest at 24°F and 12°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). From June to August the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 89% of years.

Warmth for growing adds up to 555 growing degree days a year (base 50°F), fewer than at 65% of the 37 Alaska stations. 25% of them (138) have built up by the end of June, and July adds the most, 228.

The nearest other station, Campbell Creek Sci Ctr, AK, 4 miles north of Anchorage and 655 feet lower, has a last frost 16 days later (May 28), a first frost 14 days earlier (September 12), a season 30 days shorter.

The first measurable snow (0.1 inch or more) in Anchorage usually arrives around September 29, and the last of the season around May 4. Those are the middle dates across the winters of 1991–2020 at Glen Alps, AK, 2.7 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 8 days after the last snow.

ZIP 99516 is 1 mile from Anchorage Rabbit Creek #2, AK, which stands at 913 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 99516 in zone 5b, the band where the coldest night of the year averaged -15 to -10°F (-26.1 to -23.3°C) over 1991–2020; a zone describes winter lows, not frost dates.