Frost Dates for 99929 — Wrangell, Alaska

Half of springs at Wrangell Airport, AK see their last 32°F night by April 11; only one in ten is past it by March 26, and one in ten still has one after April 29. Planting tender crops after April 19 leaves a 30% risk of a frost on them, after April 23 20%, and after April 29 10%. The 18 days between the even-odds date and the one-in-ten date is wider than at 92% of the 37 Alaska stations behind this site's ZIP pages.

In fall the first 32°F night comes by November 1 in half of years, as early as October 13 one year in ten, and holds off past November 19 one year in ten. A hard freeze of 28°F follows 17 days later, around November 18; in spring the one-in-ten date for 28°F is April 9, 20 days before the 32°F one. The freeze-free season lasts 202 days in a typical year, longer than at 97% of the 37 Alaska stations; it reaches 225 days one year in ten and falls short of 179 one year in ten. On average 83 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 19 days longer, to about April 30, and return around October 16. Nights of 24°F, cold enough to damage hardier plants, come in 100% of winters and 16°F in 81%.

July is the warmest month at Wrangell Airport, AK, averaging 64°F by day and 52°F at night; January is the coldest at 36°F and 29°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 79% of years.

Warmth for growing adds up to 821 growing degree days a year (base 50°F), more than at 76% of the 37 Alaska stations. 29% of them (237) have built up by the end of June, and July adds the most, 247.

The nearest other station, Petersburg 1, AK, 36 miles northwest of Wrangell, has a last frost 18 days later (April 29), a first frost 15 days earlier (October 17), a season 33 days shorter.

The first measurable snow (0.1 inch or more) in Wrangell usually arrives around November 11, and the last of the season around April 3. Those are the middle dates across the winters of 1991–2020 at Petersburg 1, AK, 35.6 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 99929 is 5 miles from Wrangell Airport, AK, which stands at 56 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 99929 in zone 7b, the band where the coldest night of the year averaged 5 to 10°F (-15.0 to -12.2°C) over 1991–2020; a zone describes winter lows, not frost dates.