Frost dates for 99587Girdwood, AK
The average last spring frost in Girdwood is May 8 and the average first fall frost is September 29, giving a typical growing season of about 142 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 8
- Average first fall frost
- Sep 29
- Growing season
- 142 days
Safer after May 22 (1-in-10 risk)
Possible by Sep 14 (1-in-10 risk)
Last frost typically in 193 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 12 · May 24 · Jun 5 | Sep 1 · Sep 17 · Sep 30 | 113 days | 100% |
| Frost / freeze (32°F) | Apr 26 · May 8 · May 22 | Sep 14 · Sep 29 · Oct 13 | 142 days | 100% |
| Hard freeze (28°F) | Apr 12 · Apr 26 · May 7 | Sep 27 · Oct 11 · Oct 26 | 169 days | 100% |
Planting calendar for Girdwood
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 | Apr 7 – Jun 13 |
| Tomatoes | Transplant outdoors | May 24 – Jun 9 |
| Peppers | Start seeds indoors | Apr 7 – May 8 |
| Peppers | Transplant outdoors | Jun 7 – Jul 8 |
| Eggplant | Start seeds indoors | Apr 24 – May 23 |
| Eggplant | Transplant outdoors | Jun 7 – Jul 8 |
| Cucumbers | Sow outdoors | Jun 7 – Jun 19 |
| Summer squash | Sow outdoors | May 24 – Jul 8 |
| Winter squash & pumpkins | Sow outdoors | Jun 7 – Jul 8 |
| Snap beans | Sow outdoors | May 24 – Jul 12 |
| Sweet corn | Sow outdoors | May 24 – Jun 9 |
| Watermelon & cantaloupe | Sow outdoors | Jun 7 – Jul 8 |
| Okra | Sow outdoors | May 31 – Jun 23 |
| Peas | Sow outdoors (spring) | Apr 7 – May 23 |
| Potatoes | Plant outdoors (spring) | Apr 7 – Jun 7 |
| Onions | Start seeds indoors (spring) | Feb 24 – Mar 23 |
| Onions | Transplant outdoors (spring) | Apr 24 – May 23 |
| Broccoli | Start seeds indoors (spring) | Mar 20 – Apr 23 |
| Broccoli | Transplant outdoors (spring) | Apr 24 – May 23 |
| Broccoli | Start seeds indoors (fall) | May 30 – Jun 9 |
| Broccoli | Transplant outdoors (fall) | Jun 29 – Jul 10 |
| Cabbage | Start seeds indoors (spring) | Mar 10 – Apr 7 |
| Cabbage | Transplant outdoors (spring) | Apr 7 – May 8 |
| Cabbage | Start seeds indoors (fall) | May 20 – Jun 19 |
| Cabbage | Transplant outdoors (fall) | Jun 19 – Jul 20 |
| Leaf lettuce | Sow outdoors (spring) | Apr 7 – Jun 23 |
| Leaf lettuce | Sow outdoors (fall) | Jun 19 – Aug 5 |
| Spinach | Sow outdoors (spring) | Mar 31 – May 14 |
| Spinach | Sow outdoors (fall) | Jul 6 – Aug 10 |
| Radishes | Sow outdoors (spring) | Apr 7 – May 28 |
| Radishes | Sow outdoors (fall) | Jun 19 – Aug 20 |
| Kale | Sow outdoors (spring) | Apr 24 – May 14 |
| Kale | Sow outdoors (fall) | Jun 12 – Jul 20 |
| Carrots | Sow outdoors (spring) | May 8 – Jun 23 |
| Carrots | Sow outdoors (fall) | May 20 – Jul 5 |
| Garlic | Plant outdoors (fall) | Sep 19 – Oct 20 |
Where these dates come from
ZIP code 99587 is matched to the NOAA station Alyeska, AK, 1.6 km away, at 272 ft elevation (167 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Alyeska, AK (used) | 272 ft | May 8 | Sep 29 |
| Portage Glacier V C, AK | 103 ft | May 27 | Sep 12 |
| Hope, AK | 180 ft | May 18 | Sep 24 |
| Eagle Rvr Nature Ctr, AK | 520 ft | May 16 | Sep 20 |
Frost dates near Girdwood
- Hope, AK 99605 · last May 18, first Sep 23
- Anchorage, AK 99519 · last May 18, first Sep 23
- Indian, AK 99540 · last May 18, first Sep 23
- Whittier, AK 99693 · last Apr 25, first Oct 14
- Moose Pass, AK 99631 · last May 31, first Sep 8
- Eagle River, AK 99577 · last May 9, first Sep 26
- Chugiak, AK 99567 · last May 21, first Sep 15
- Cooper Landing, AK 99572 · last Jun 12, first Sep 1
Frequently asked questions
- When is the last frost in Girdwood, AK?
- For ZIP code 99587, the average last spring frost (32°F) is May 8, based on NOAA 1991-2020 climate normals for the Alyeska, AK weather station. There is a 1-in-10 chance of a frost after May 22.
- When is the first frost in Girdwood, AK?
- The average first fall frost (32°F) is September 29. There is a 1-in-10 chance of frost by September 14, so tender plants are at risk from that point on.
- How long is the growing season in 99587?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 142 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.