Frost dates for 98537Cosmopolis, WA
The average last spring frost in Cosmopolis is March 29 and the average first fall frost is November 15, giving a typical growing season of about 234 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Mar 29
- Average first fall frost
- Nov 15
- Growing season
- 234 days
Safer after Apr 20 (1-in-10 risk)
Possible by Oct 27 (1-in-10 risk)
First frost typically in 15 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) | Apr 4 · Apr 23 · May 11 | Oct 11 · Oct 27 · Nov 14 | 187 days | 100% |
| Frost / freeze (32°F) | Feb 25 · Mar 29 · Apr 20 | Oct 27 · Nov 15 · Dec 10 | 234 days | 100% |
| Hard freeze (28°F) | Dec 27 · Feb 18 · Mar 20 | Nov 11 · Dec 6 · Jan 26 | 304 days | 95% |
Planting calendar for Cosmopolis
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 | Feb 26 – May 4 |
| Tomatoes | Transplant outdoors | Apr 14 – Jul 26 |
| Peppers | Start seeds indoors | Feb 26 – Mar 29 |
| Peppers | Transplant outdoors | Apr 28 – May 29 |
| Eggplant | Start seeds indoors | Mar 15 – Apr 13 |
| Eggplant | Transplant outdoors | Apr 28 – May 29 |
| Cucumbers | Sow outdoors | Apr 28 – Aug 5 |
| Summer squash | Sow outdoors | Apr 14 – May 29 |
| Winter squash & pumpkins | Sow outdoors | Apr 28 – May 29 |
| Snap beans | Sow outdoors | Apr 14 – Aug 28 |
| Sweet corn | Sow outdoors | Apr 14 – Jul 26 |
| Watermelon & cantaloupe | Sow outdoors | Apr 28 – May 29 |
| Okra | Sow outdoors | Apr 21 – May 14 |
| Peas | Sow outdoors (spring) | Feb 26 – Apr 13 |
| Potatoes | Plant outdoors (spring) | Feb 26 – Apr 28 |
| Onions | Start seeds indoors (spring) | Jan 15 – Feb 11 |
| Onions | Transplant outdoors (spring) | Mar 15 – Apr 13 |
| Broccoli | Start seeds indoors (spring) | Feb 8 – Mar 14 |
| Broccoli | Transplant outdoors (spring) | Mar 15 – Apr 13 |
| Broccoli | Start seeds indoors (fall) | Jul 16 – Jul 26 |
| Broccoli | Transplant outdoors (fall) | Aug 15 – Aug 26 |
| Cabbage | Start seeds indoors (spring) | Jan 29 – Feb 26 |
| Cabbage | Transplant outdoors (spring) | Feb 26 – Mar 29 |
| Cabbage | Start seeds indoors (fall) | Jul 6 – Aug 5 |
| Cabbage | Transplant outdoors (fall) | Aug 5 – Sep 5 |
| Leaf lettuce | Sow outdoors (spring) | Feb 26 – May 14 |
| Leaf lettuce | Sow outdoors (fall) | Aug 5 – Sep 21 |
| Spinach | Sow outdoors (spring) | Feb 19 – Apr 4 |
| Spinach | Sow outdoors (fall) | Aug 22 – Sep 26 |
| Radishes | Sow outdoors (spring) | Feb 26 – Apr 18 |
| Radishes | Sow outdoors (fall) | Aug 5 – Oct 6 |
| Kale | Sow outdoors (spring) | Mar 15 – Apr 4 |
| Kale | Sow outdoors (fall) | Jul 29 – Sep 5 |
| Carrots | Sow outdoors (spring) | Mar 29 – May 14 |
| Carrots | Sow outdoors (fall) | Jul 6 – Aug 21 |
| Garlic | Plant outdoors (fall) | Nov 5 – Dec 6 |
Where these dates come from
ZIP code 98537 is matched to the NOAA station Aberdeen, WA, 4.4 km away, at 10 ft elevation (13 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Aberdeen, WA (used) | 10 ft | Mar 29 | Nov 15 |
| Hoquiam Bowerman Ap, WA | 12 ft | Mar 30 | Nov 14 |
| Elma, WA | 70 ft | May 1 | Oct 14 |
| Grayland, WA | 10 ft | Mar 29 | Nov 7 |
Frost dates near Cosmopolis
- Aberdeen, WA 98520 · last Mar 29, first Nov 15
- Hoquiam, WA 98550 · last Mar 30, first Nov 14
- Satsop, WA 98583 · last May 1, first Oct 14
- Montesano, WA 98563 · last May 1, first Oct 14
- Westport, WA 98595 · last Mar 29, first Nov 7
- Grayland, WA 98547 · last Mar 29, first Nov 7
- Elma, WA 98541 · last May 1, first Oct 14
- Ocean Shores, WA 98569 · last Mar 30, first Nov 14
Frequently asked questions
- When is the last frost in Cosmopolis, WA?
- For ZIP code 98537, the average last spring frost (32°F) is March 29, based on NOAA 1991-2020 climate normals for the Aberdeen, WA weather station. There is a 1-in-10 chance of a frost after April 20.
- When is the first frost in Cosmopolis, WA?
- The average first fall frost (32°F) is November 15. There is a 1-in-10 chance of frost by October 27, so tender plants are at risk from that point on.
- How long is the growing season in 98537?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 234 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.