Frost dates for 99403Clarkston, WA
The average last spring frost in Clarkston is April 6 and the average first fall frost is October 26, giving a typical growing season of about 200 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 6
- Average first fall frost
- Oct 26
- Growing season
- 200 days
Safer after Apr 26 (1-in-10 risk)
Possible by Oct 10 (1-in-10 risk)
Last frost typically in 154 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 11 · Apr 29 · May 12 | Oct 1 · Oct 13 · Oct 28 | 170 days | 100% |
| Frost / freeze (32°F) | Mar 20 · Apr 6 · Apr 26 | Oct 10 · Oct 26 · Nov 12 | 200 days | 100% |
| Hard freeze (28°F) | Feb 25 · Mar 15 · Apr 4 | Oct 20 · Nov 8 · Nov 28 | 235 days | 100% |
Planting calendar for Clarkston
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 6 – May 12 |
| Tomatoes | Transplant outdoors | Apr 22 – Jul 6 |
| Peppers | Start seeds indoors | Mar 6 – Apr 6 |
| Peppers | Transplant outdoors | May 6 – Jun 6 |
| Eggplant | Start seeds indoors | Mar 23 – Apr 21 |
| Eggplant | Transplant outdoors | May 6 – Jun 6 |
| Cucumbers | Sow outdoors | May 6 – Jul 16 |
| Summer squash | Sow outdoors | Apr 22 – Jun 6 |
| Winter squash & pumpkins | Sow outdoors | May 6 – Jun 6 |
| Snap beans | Sow outdoors | Apr 22 – Aug 8 |
| Sweet corn | Sow outdoors | Apr 22 – Jul 6 |
| Watermelon & cantaloupe | Sow outdoors | May 6 – Jun 6 |
| Okra | Sow outdoors | Apr 29 – May 22 |
| Peas | Sow outdoors (spring) | Mar 6 – Apr 21 |
| Potatoes | Plant outdoors (spring) | Mar 6 – May 6 |
| Onions | Start seeds indoors (spring) | Jan 23 – Feb 19 |
| Onions | Transplant outdoors (spring) | Mar 23 – Apr 21 |
| Broccoli | Start seeds indoors (spring) | Feb 16 – Mar 22 |
| Broccoli | Transplant outdoors (spring) | Mar 23 – Apr 21 |
| Broccoli | Start seeds indoors (fall) | Jun 26 – Jul 6 |
| Broccoli | Transplant outdoors (fall) | Jul 26 – Aug 6 |
| Cabbage | Start seeds indoors (spring) | Feb 6 – Mar 6 |
| Cabbage | Transplant outdoors (spring) | Mar 6 – Apr 6 |
| Cabbage | Start seeds indoors (fall) | Jun 16 – Jul 16 |
| Cabbage | Transplant outdoors (fall) | Jul 16 – Aug 16 |
| Leaf lettuce | Sow outdoors (spring) | Mar 6 – May 22 |
| Leaf lettuce | Sow outdoors (fall) | Jul 16 – Sep 1 |
| Spinach | Sow outdoors (spring) | Feb 27 – Apr 12 |
| Spinach | Sow outdoors (fall) | Aug 2 – Sep 6 |
| Radishes | Sow outdoors (spring) | Mar 6 – Apr 26 |
| Radishes | Sow outdoors (fall) | Jul 16 – Sep 16 |
| Kale | Sow outdoors (spring) | Mar 23 – Apr 12 |
| Kale | Sow outdoors (fall) | Jul 9 – Aug 16 |
| Carrots | Sow outdoors (spring) | Apr 6 – May 22 |
| Carrots | Sow outdoors (fall) | Jun 16 – Aug 1 |
| Garlic | Plant outdoors (fall) | Oct 16 – Nov 16 |
Where these dates come from
ZIP code 99403 is matched to the NOAA station Lewiston Nez Perce Co Ap, ID, 4.4 km away, at 1,436 ft elevation (442 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Lewiston Nez Perce Co Ap, ID (used) | 1,436 ft | Apr 6 | Oct 26 |
| Moscow U Of I, ID | 2,660 ft | — | — |
| Winchester, ID | 3,972 ft | May 23 | Sep 25 |
| Pullman Moscow Rgnl Ap, WA | 2,551 ft | Apr 29 | Oct 2 |
Frost dates near Clarkston
- Uniontown, WA 99179 · last —, first —
- Lewiston, ID 83501 · last Apr 6, first Oct 26
- Lapwai, ID 83540 · last Apr 6, first Oct 26
- Genesee, ID 83832 · last —, first —
- Colton, WA 99113 · last Apr 29, first Oct 2
- Asotin, WA 99402 · last Jun 8, first Sep 5
- Anatone, WA 99401 · last Jun 8, first Sep 5
- Culdesac, ID 83524 · last Apr 6, first Oct 26
Frequently asked questions
- When is the last frost in Clarkston, WA?
- For ZIP code 99403, the average last spring frost (32°F) is April 6, based on NOAA 1991-2020 climate normals for the Lewiston Nez Perce Co Ap, ID weather station. There is a 1-in-10 chance of a frost after April 26.
- When is the first frost in Clarkston, WA?
- The average first fall frost (32°F) is October 26. There is a 1-in-10 chance of frost by October 10, so tender plants are at risk from that point on.
- How long is the growing season in 99403?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 200 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.