USDA Hardiness Zone 7a
Frost Dates for 99362 — Walla Walla, Washington
Averages from Walla Walla Rgnl Ap, Wa US, the nearest reporting station, 12.4 miles away.
Plant tender crops after March 27, and expect the first autumn freeze around October 31. That leaves about 219 frost-free days.
- Last spring frost
- March 27
- First fall frost
- October 31
- Growing season
- 219 days
- Hardiness zone
- 7a
50% probability
50% probability
frost-free
0 to 5°F annual low
Planting calendar for 99362
| When | What to do |
|---|---|
| January 16 – January 30 | Start peppers and aubergines indoors They need eight to ten weeks under lights before they can go out. |
| January 30 – February 13 | Start tomatoes indoors Six to eight weeks gives a transplant big enough to set fruit early. |
| February 27 – March 13 | Sow peas, spinach, lettuce, radish outdoors These tolerate light frost and prefer to germinate in cool soil. |
| March 27 onward | Transplant tomatoes, peppers, basil, squash, cucumbers The average last freeze has passed — still watch the actual forecast. |
| by August 8 | Sow the autumn crop of carrots, beets and brassicas They need about twelve weeks to size up before growth stops. |
| by October 17 | Harvest tender crops, or be ready to cover them A first freeze two weeks early is well within normal variation. |
| October 31 onward | Plant garlic, mulch beds, lift tender bulbs Garlic wants a cold spell; bare soil loses structure over winter. |
What these dates mean
Wait until after March 27 to put tender plants — tomatoes, peppers, basil, squash — in the ground. That is the date by which half of years in Walla Walla, Washington are past their last freeze. Harvest before October 31, which leaves roughly 219 frost-free days.
ZIP 99362 sits in USDA hardiness zone 7a, meaning the average coldest night of the year falls between 0 to 5°F. Zone decides what survives the winter; frost dates decide when to plant each spring. They are different questions, and a plant can pass one and fail the other.
These are thirty-year NOAA averages for 1991–2020, not a forecast. Any individual year can frost two to three weeks either side of these dates, so check the actual forecast before planting out.