Frost dates for 99653Port Alsworth, AK
The average last spring frost in Port Alsworth is May 12 and the average first fall frost is September 24, giving a typical growing season of about 134 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 12
- Average first fall frost
- Sep 24
- Growing season
- 134 days
Safer after May 27 (1-in-10 risk)
Possible by Sep 8 (1-in-10 risk)
Last frost typically in 197 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 14 · May 27 · Jun 6 | Aug 26 · Sep 10 · Sep 24 | 107 days | 100% |
| Frost / freeze (32°F) | Apr 29 · May 12 · May 27 | Sep 8 · Sep 24 · Oct 7 | 134 days | 100% |
| Hard freeze (28°F) | Apr 15 · Apr 29 · May 14 | Sep 20 · Oct 4 · Oct 22 | 160 days | 100% |
Planting calendar for Port Alsworth
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 11 – Jun 17 |
| Tomatoes | Transplant outdoors | May 28 – Jun 4 |
| Peppers | Start seeds indoors | Apr 11 – May 12 |
| Peppers | Transplant outdoors | Jun 11 – Jul 12 |
| Eggplant | Start seeds indoors | Apr 28 – May 27 |
| Eggplant | Transplant outdoors | Jun 11 – Jul 12 |
| Cucumbers | Sow outdoors | Jun 11 – Jun 14 |
| Summer squash | Sow outdoors | May 28 – Jul 12 |
| Winter squash & pumpkins | Sow outdoors | Jun 11 – Jul 12 |
| Snap beans | Sow outdoors | May 28 – Jul 7 |
| Sweet corn | Sow outdoors | May 28 – Jun 4 |
| Watermelon & cantaloupe | Sow outdoors | Jun 11 – Jul 12 |
| Okra | Sow outdoors | Jun 4 – Jun 27 |
| Peas | Sow outdoors (spring) | Apr 11 – May 27 |
| Potatoes | Plant outdoors (spring) | Apr 11 – Jun 11 |
| Onions | Start seeds indoors (spring) | Feb 28 – Mar 27 |
| Onions | Transplant outdoors (spring) | Apr 28 – May 27 |
| Broccoli | Start seeds indoors (spring) | Mar 24 – Apr 27 |
| Broccoli | Transplant outdoors (spring) | Apr 28 – May 27 |
| Broccoli | Start seeds indoors (fall) | May 25 – Jun 4 |
| Broccoli | Transplant outdoors (fall) | Jun 24 – Jul 5 |
| Cabbage | Start seeds indoors (spring) | Mar 14 – Apr 11 |
| Cabbage | Transplant outdoors (spring) | Apr 11 – May 12 |
| Cabbage | Start seeds indoors (fall) | May 15 – Jun 14 |
| Cabbage | Transplant outdoors (fall) | Jun 14 – Jul 15 |
| Leaf lettuce | Sow outdoors (spring) | Apr 11 – Jun 27 |
| Leaf lettuce | Sow outdoors (fall) | Jun 14 – Jul 31 |
| Spinach | Sow outdoors (spring) | Apr 4 – May 18 |
| Spinach | Sow outdoors (fall) | Jul 1 – Aug 5 |
| Radishes | Sow outdoors (spring) | Apr 11 – Jun 1 |
| Radishes | Sow outdoors (fall) | Jun 14 – Aug 15 |
| Kale | Sow outdoors (spring) | Apr 28 – May 18 |
| Kale | Sow outdoors (fall) | Jun 7 – Jul 15 |
| Carrots | Sow outdoors (spring) | May 12 – Jun 27 |
| Carrots | Sow outdoors (fall) | May 15 – Jun 30 |
| Garlic | Plant outdoors (fall) | Sep 14 – Oct 15 |
Where these dates come from
ZIP code 99653 is matched to the NOAA station Port Alsworth, AK, 0.2 km away, at 260 ft elevation (14 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Port Alsworth, AK (used) | 260 ft | May 12 | Sep 24 |
| Port Alsworth 1 Sw, AK | 321 ft | Jun 2 | Sep 12 |
| Iliamna Ap, AK | 143 ft | May 10 | Oct 1 |
| Intricate Bay, AK | 120 ft | Jun 4 | Sep 12 |
Frost dates near Port Alsworth
- Nondalton, AK 99640 · last May 10, first Oct 1
- Pedro Bay, AK 99647 · last May 12, first Sep 24
- Iliamna, AK 99606 · last May 10, first Oct 1
Frequently asked questions
- When is the last frost in Port Alsworth, AK?
- For ZIP code 99653, the average last spring frost (32°F) is May 12, based on NOAA 1991-2020 climate normals for the Port Alsworth, AK weather station. There is a 1-in-10 chance of a frost after May 27.
- When is the first frost in Port Alsworth, AK?
- The average first fall frost (32°F) is September 24. There is a 1-in-10 chance of frost by September 8, so tender plants are at risk from that point on.
- How long is the growing season in 99653?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 134 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.