Frost dates for 99672Sterling, AK
The average last spring frost in Sterling is May 20 and the average first fall frost is September 21, giving a typical growing season of about 123 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 20
- Average first fall frost
- Sep 21
- Growing season
- 123 days
Safer after Jun 1 (1-in-10 risk)
Possible by Sep 6 (1-in-10 risk)
Last frost typically in 198 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 25 · Jun 4 · Jun 15 | Aug 26 · Sep 8 · Sep 23 | 94 days | 100% |
| Frost / freeze (32°F) | May 6 · May 20 · Jun 1 | Sep 6 · Sep 21 · Oct 4 | 123 days | 100% |
| Hard freeze (28°F) | Apr 19 · May 3 · May 17 | Sep 17 · Sep 30 · Oct 15 | 148 days | 100% |
Planting calendar for Sterling
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 19 – Jun 25 |
| Tomatoes | Transplant outdoors | Jun 5 – Jun 1 |
| Peppers | Start seeds indoors | Apr 19 – May 20 |
| Peppers | Transplant outdoors | Jun 19 – Jul 20 |
| Eggplant | Start seeds indoors | May 6 – Jun 4 |
| Eggplant | Transplant outdoors | Jun 19 – Jul 20 |
| Cucumbers | Sow outdoors | Jun 19 – Jun 11 |
| Summer squash | Sow outdoors | Jun 5 – Jul 20 |
| Winter squash & pumpkins | Sow outdoors | Jun 19 – Jul 20 |
| Snap beans | Sow outdoors | Jun 5 – Jul 4 |
| Sweet corn | Sow outdoors | Jun 5 – Jun 1 |
| Watermelon & cantaloupe | Sow outdoors | Jun 19 – Jul 20 |
| Okra | Sow outdoors | Jun 12 – Jul 5 |
| Peas | Sow outdoors (spring) | Apr 19 – Jun 4 |
| Potatoes | Plant outdoors (spring) | Apr 19 – Jun 19 |
| Onions | Start seeds indoors (spring) | Mar 8 – Apr 4 |
| Onions | Transplant outdoors (spring) | May 6 – Jun 4 |
| Broccoli | Start seeds indoors (spring) | Apr 1 – May 5 |
| Broccoli | Transplant outdoors (spring) | May 6 – Jun 4 |
| Broccoli | Start seeds indoors (fall) | May 22 – Jun 1 |
| Broccoli | Transplant outdoors (fall) | Jun 21 – Jul 2 |
| Cabbage | Start seeds indoors (spring) | Mar 22 – Apr 19 |
| Cabbage | Transplant outdoors (spring) | Apr 19 – May 20 |
| Cabbage | Start seeds indoors (fall) | May 12 – Jun 11 |
| Cabbage | Transplant outdoors (fall) | Jun 11 – Jul 12 |
| Leaf lettuce | Sow outdoors (spring) | Apr 19 – Jul 5 |
| Leaf lettuce | Sow outdoors (fall) | Jun 11 – Jul 28 |
| Spinach | Sow outdoors (spring) | Apr 12 – May 26 |
| Spinach | Sow outdoors (fall) | Jun 28 – Aug 2 |
| Radishes | Sow outdoors (spring) | Apr 19 – Jun 9 |
| Radishes | Sow outdoors (fall) | Jun 11 – Aug 12 |
| Kale | Sow outdoors (spring) | May 6 – May 26 |
| Kale | Sow outdoors (fall) | Jun 4 – Jul 12 |
| Carrots | Sow outdoors (spring) | May 20 – Jul 5 |
| Carrots | Sow outdoors (fall) | May 12 – Jun 27 |
| Garlic | Plant outdoors (fall) | Sep 11 – Oct 12 |
Where these dates come from
ZIP code 99672 is matched to the NOAA station Sterling 6Sw, AK, 4.4 km away, at 292 ft elevation (23 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Sterling 6Sw, AK (used) | 292 ft | May 20 | Sep 21 |
| Soldotna 5Ssw, AK | 180 ft | Jun 11 | Sep 1 |
| Kenai Muni Ap, AK | 91 ft | May 24 | Sep 12 |
| Kenai 9N, AK | 126 ft | May 18 | Sep 22 |
Frost dates near Sterling
- Soldotna, AK 99669 · last Jun 11, first Sep 1
- Kenai, AK 99611 · last May 24, first Sep 12
- Nikiski, AK 99635 · last May 18, first Sep 22
- Kasilof, AK 99610 · last Jun 11, first Sep 1
- Clam Gulch, AK 99568 · last Jun 11, first Sep 1
- Cooper Landing, AK 99572 · last Jun 12, first Sep 1
- Tyonek, AK 99682 · last May 18, first Sep 22
- Ninilchik, AK 99639 · last May 10, first Sep 29
Frequently asked questions
- When is the last frost in Sterling, AK?
- For ZIP code 99672, the average last spring frost (32°F) is May 20, based on NOAA 1991-2020 climate normals for the Sterling 6Sw, AK weather station. There is a 1-in-10 chance of a frost after June 1.
- When is the first frost in Sterling, AK?
- The average first fall frost (32°F) is September 21. There is a 1-in-10 chance of frost by September 6, so tender plants are at risk from that point on.
- How long is the growing season in 99672?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 123 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.