When is the last frost in Glennallen, AK?

For ZIP code 99588, the average last spring frost (32°F) is June 7, based on NOAA 1991-2020 climate normals for the Gulkana Ap, AK weather station. There is a 1-in-10 chance of a frost after July 5.

When is the first frost in Glennallen, AK?

The average first fall frost (32°F) is August 21. There is a 1-in-10 chance of frost by August 8, so tender plants are at risk from that point on.

How long is the growing season in 99588?

In half of years, the frost-free season (between the last and first 32°F frost) is at least 73 days long.

Are these frost dates a forecast?

No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.

Frost dates for 99588Glennallen, AK

The average last spring frost in Glennallen is June 7 and the average first fall frost is August 21, giving a typical growing season of about 73 days. Dates are based on NOAA 1991-2020 climate normals.

Average last spring frost: Jun 7
Average first fall frost: Aug 21
Growing season: 73 days

Frost risk by date

NOAA reports frost dates as probabilities. The middle date is the average (a 50% chance). For spring, the 10% date is a safer planting date: frost after it happens in about 1 year in 10. Light frost (36°F) can damage tender plants; a hard freeze (28°F) kills most annuals.

Spring dates: chance of a frost AFTER the date. Fall dates: chance of a frost BEFORE the date.
Temperature	Last spring: 90% / 50% / 10% chance	First fall: 10% / 50% / 90% chance	Growing season (50%)	Years with at least one
Light frost (36°F)	—	—	39 days	100%
Frost / freeze (32°F)	May 24 · Jun 7 · Jul 5	Aug 8 · Aug 21 · Sep 3	73 days	100%
Hard freeze (28°F)	May 5 · May 19 · Jun 3	Aug 19 · Sep 2 · Sep 17	105 days	100%

Where these dates come from

ZIP code 99588 is matched to the NOAA station Gulkana Ap, AK, 12.2 km away, at 1,562 ft elevation (52 ft lower than the ZIP code's center). Nearby stations for comparison:

Station	Elevation	Avg last frost	Avg first frost
Gulkana Ap, AK (used)	1,562 ft	Jun 7	Aug 21
Gennallen Kcam, AK	1,383 ft	—	—
Tonsina, AK	1,579 ft	—	—
Lake Susitna, AK	2,375 ft	May 30	Sep 4

Frost dates near Glennallen

Copper Center, AK 99573 · last —, first —
Gakona, AK 99586 · last Jun 7, first Aug 21
Chitina, AK 99566 · last May 31, first Sep 3

Frequently asked questions

When is the last frost in Glennallen, AK?: For ZIP code 99588, the average last spring frost (32°F) is June 7, based on NOAA 1991-2020 climate normals for the Gulkana Ap, AK weather station. There is a 1-in-10 chance of a frost after July 5.
When is the first frost in Glennallen, AK?: The average first fall frost (32°F) is August 21. There is a 1-in-10 chance of frost by August 8, so tender plants are at risk from that point on.
How long is the growing season in 99588?: In half of years, the frost-free season (between the last and first 32°F frost) is at least 73 days long.
Are these frost dates a forecast?: No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.