Frost dates for 99520Anchorage, AK
The average last spring frost in Anchorage is May 1 and the average first fall frost is September 29, giving a typical growing season of about 150 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 1
- Average first fall frost
- Sep 29
- Growing season
- 150 days
Safer after May 9 (1-in-10 risk)
Possible by Sep 17 (1-in-10 risk)
Last frost typically in 196 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.
| 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) | May 2 · May 12 · May 23 | Sep 7 · Sep 20 · Sep 30 | 129 days | 100% |
| Frost / freeze (32°F) | Apr 19 · May 1 · May 9 | Sep 17 · Sep 29 · Oct 12 | 150 days | 100% |
| Hard freeze (28°F) | Apr 10 · Apr 19 · May 1 | Sep 27 · Oct 8 · Oct 21 | 172 days | 100% |
Planting calendar for Anchorage
Planting windows from the University of Maryland Extension calendar, shifted to your average frost dates. Use them as a starting point and adjust for seed packet instructions and local conditions.
| Crop | Task | Window |
|---|---|---|
| Tomatoes | Start seeds indoors | Mar 31 – Jun 6 |
| Tomatoes | Transplant outdoors | May 17 – Jun 9 |
| Peppers | Start seeds indoors | Mar 31 – May 1 |
| Peppers | Transplant outdoors | May 31 – Jul 1 |
| Eggplant | Start seeds indoors | Apr 17 – May 16 |
| Eggplant | Transplant outdoors | May 31 – Jul 1 |
| Cucumbers | Sow outdoors | May 31 – Jun 19 |
| Summer squash | Sow outdoors | May 17 – Jul 1 |
| Winter squash & pumpkins | Sow outdoors | May 31 – Jul 1 |
| Snap beans | Sow outdoors | May 17 – Jul 12 |
| Sweet corn | Sow outdoors | May 17 – Jun 9 |
| Watermelon & cantaloupe | Sow outdoors | May 31 – Jul 1 |
| Okra | Sow outdoors | May 24 – Jun 16 |
| Peas | Sow outdoors (spring) | Mar 31 – May 16 |
| Potatoes | Plant outdoors (spring) | Mar 31 – May 31 |
| Onions | Start seeds indoors (spring) | Feb 17 – Mar 16 |
| Onions | Transplant outdoors (spring) | Apr 17 – May 16 |
| Broccoli | Start seeds indoors (spring) | Mar 13 – Apr 16 |
| Broccoli | Transplant outdoors (spring) | Apr 17 – May 16 |
| Broccoli | Start seeds indoors (fall) | May 30 – Jun 9 |
| Broccoli | Transplant outdoors (fall) | Jun 29 – Jul 10 |
| Cabbage | Start seeds indoors (spring) | Mar 3 – Mar 31 |
| Cabbage | Transplant outdoors (spring) | Mar 31 – May 1 |
| Cabbage | Start seeds indoors (fall) | May 20 – Jun 19 |
| Cabbage | Transplant outdoors (fall) | Jun 19 – Jul 20 |
| Leaf lettuce | Sow outdoors (spring) | Mar 31 – Jun 16 |
| Leaf lettuce | Sow outdoors (fall) | Jun 19 – Aug 5 |
| Spinach | Sow outdoors (spring) | Mar 24 – May 7 |
| Spinach | Sow outdoors (fall) | Jul 6 – Aug 10 |
| Radishes | Sow outdoors (spring) | Mar 31 – May 21 |
| Radishes | Sow outdoors (fall) | Jun 19 – Aug 20 |
| Kale | Sow outdoors (spring) | Apr 17 – May 7 |
| Kale | Sow outdoors (fall) | Jun 12 – Jul 20 |
| Carrots | Sow outdoors (spring) | May 1 – Jun 16 |
| Carrots | Sow outdoors (fall) | May 20 – Jul 5 |
| Garlic | Plant outdoors (fall) | Sep 19 – Oct 20 |
Where these dates come from
ZIP code 99520 is matched to the NOAA station Anchorage Merrill Fld, AK, 2.4 km away, at 138 ft elevation (33 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Anchorage Merrill Fld, AK (used) | 138 ft | May 1 | Sep 29 |
| Anchorage Lake Hood Ap, AK | 90 ft | May 1 | Oct 3 |
| Anchorage Forecast Office, AK | 131 ft | May 5 | Sep 29 |
| Anchorage Intl Ap, AK | 120 ft | May 5 | Oct 1 |
Frost dates near Anchorage
- Anchorage, AK 99509 · last May 1, first Sep 29
- Eagle River, AK 99577 · last May 9, first Sep 26
- Indian, AK 99540 · last May 18, first Sep 23
- Chugiak, AK 99567 · last May 21, first Sep 15
- Big Lake, AK 99652 · last May 29, first Sep 7
- Wasilla, AK 99623 · last May 16, first Sep 23
- Hope, AK 99605 · last May 18, first Sep 23
- Houston, AK 99694 · last May 29, first Sep 7
Frequently asked questions
- When is the last frost in Anchorage, AK?
- For ZIP code 99520, the average last spring frost (32°F) is May 1, based on NOAA 1991-2020 climate normals for the Anchorage Merrill Fld, AK weather station. There is a 1-in-10 chance of a frost after May 9.
- When is the first frost in Anchorage, AK?
- The average first fall frost (32°F) is September 29. There is a 1-in-10 chance of frost by September 17, so tender plants are at risk from that point on.
- How long is the growing season in 99520?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 150 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.