Frost dates for 99362Walla Walla, WA
The average last spring frost in Walla Walla is March 27 and the average first fall frost is October 31, giving a typical growing season of about 219 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Mar 27
- Average first fall frost
- Oct 31
- Growing season
- 219 days
Safer after Apr 22 (1-in-10 risk)
Possible by Oct 15 (1-in-10 risk)
Last frost typically in 145 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 2 · Apr 21 · May 8 | Oct 4 · Oct 19 · Nov 2 | 180 days | 100% |
| Frost / freeze (32°F) | Mar 3 · Mar 27 · Apr 22 | Oct 15 · Oct 31 · Nov 17 | 219 days | 100% |
| Hard freeze (28°F) | Feb 9 · Mar 4 · Mar 27 | Oct 25 · Nov 14 · Dec 4 | 253 days | 100% |
Planting calendar for Walla Walla
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 24 – May 2 |
| Tomatoes | Transplant outdoors | Apr 12 – Jul 11 |
| Peppers | Start seeds indoors | Feb 24 – Mar 27 |
| Peppers | Transplant outdoors | Apr 26 – May 27 |
| Eggplant | Start seeds indoors | Mar 13 – Apr 11 |
| Eggplant | Transplant outdoors | Apr 26 – May 27 |
| Cucumbers | Sow outdoors | Apr 26 – Jul 21 |
| Summer squash | Sow outdoors | Apr 12 – May 27 |
| Winter squash & pumpkins | Sow outdoors | Apr 26 – May 27 |
| Snap beans | Sow outdoors | Apr 12 – Aug 13 |
| Sweet corn | Sow outdoors | Apr 12 – Jul 11 |
| Watermelon & cantaloupe | Sow outdoors | Apr 26 – May 27 |
| Okra | Sow outdoors | Apr 19 – May 12 |
| Peas | Sow outdoors (spring) | Feb 24 – Apr 11 |
| Potatoes | Plant outdoors (spring) | Feb 24 – Apr 26 |
| Onions | Start seeds indoors (spring) | Jan 13 – Feb 9 |
| Onions | Transplant outdoors (spring) | Mar 13 – Apr 11 |
| Broccoli | Start seeds indoors (spring) | Feb 6 – Mar 12 |
| Broccoli | Transplant outdoors (spring) | Mar 13 – Apr 11 |
| Broccoli | Start seeds indoors (fall) | Jul 1 – Jul 11 |
| Broccoli | Transplant outdoors (fall) | Jul 31 – Aug 11 |
| Cabbage | Start seeds indoors (spring) | Jan 27 – Feb 24 |
| Cabbage | Transplant outdoors (spring) | Feb 24 – Mar 27 |
| Cabbage | Start seeds indoors (fall) | Jun 21 – Jul 21 |
| Cabbage | Transplant outdoors (fall) | Jul 21 – Aug 21 |
| Leaf lettuce | Sow outdoors (spring) | Feb 24 – May 12 |
| Leaf lettuce | Sow outdoors (fall) | Jul 21 – Sep 6 |
| Spinach | Sow outdoors (spring) | Feb 17 – Apr 2 |
| Spinach | Sow outdoors (fall) | Aug 7 – Sep 11 |
| Radishes | Sow outdoors (spring) | Feb 24 – Apr 16 |
| Radishes | Sow outdoors (fall) | Jul 21 – Sep 21 |
| Kale | Sow outdoors (spring) | Mar 13 – Apr 2 |
| Kale | Sow outdoors (fall) | Jul 14 – Aug 21 |
| Carrots | Sow outdoors (spring) | Mar 27 – May 12 |
| Carrots | Sow outdoors (fall) | Jun 21 – Aug 6 |
| Garlic | Plant outdoors (fall) | Oct 21 – Nov 21 |
Where these dates come from
ZIP code 99362 is matched to the NOAA station Walla Walla Rgnl Ap, WA, 5.1 km away, at 1,166 ft elevation (195 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Walla Walla Rgnl Ap, WA (used) | 1,166 ft | Mar 27 | Oct 31 |
| Whitman Mission, WA | 632 ft | May 2 | Oct 1 |
| Milton Freewater, OR | 970 ft | Mar 25 | Oct 29 |
| Dayton 1 Wsw, WA | 1,557 ft | Apr 28 | Oct 13 |
Frost dates near Walla Walla
- College Place, WA 99324 · last May 2, first Oct 1
- Milton Freewater, OR 97862 · last Mar 25, first Oct 29
- Dixie, WA 99329 · last Apr 28, first Oct 13
- Touchet, WA 99360 · last May 2, first Oct 1
- Waitsburg, WA 99361 · last Apr 28, first Oct 13
- Weston, OR 97886 · last May 12, first Sep 27
- Athena, OR 97813 · last May 12, first Sep 27
- Prescott, WA 99348 · last Apr 28, first Oct 13
Frequently asked questions
- When is the last frost in Walla Walla, WA?
- For ZIP code 99362, the average last spring frost (32°F) is March 27, based on NOAA 1991-2020 climate normals for the Walla Walla Rgnl Ap, WA weather station. There is a 1-in-10 chance of a frost after April 22.
- When is the first frost in Walla Walla, WA?
- The average first fall frost (32°F) is October 31. There is a 1-in-10 chance of frost by October 15, so tender plants are at risk from that point on.
- How long is the growing season in 99362?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 219 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.