Frost Dates for Sumner, WA 98390
Last spring frost April 19 · First fall frost October 20 · 184 frost-free days · USDA Zone 8b
Frost probability for 98390
| Frost | 10% | 50% | 90% |
|---|---|---|---|
| Spring (last frost) | May 9 | April 19 | March 30 |
| Fall (first frost) | October 2 | October 20 | November 5 |
Dates come from NOAA 1971–2000 freeze probabilities at the nearest reporting station (17.7 km away); the 50% date is the median year.
Month by month in Sumner
| Month | What to do |
|---|---|
| January | Plan your garden layout and order seeds. Research varieties suited to your frost dates. |
| February | Start peppers and eggplant indoors 8–10 weeks before your last frost (around April 19). Start tomatoes about two weeks later, 6–8 weeks before last frost. |
| March | Start herbs, basil, and squash indoors (4–6 weeks before frost). Direct sow peas, spinach, and lettuce if soil is workable. |
| April | Last frost around April 19. Transplant cold-hardy crops (broccoli, kale, cabbage). Harden off tomato and pepper seedlings. |
| May | Frost has passed. Transplant tomatoes, peppers, and basil outdoors. Direct sow beans, cucumbers, squash, and zucchini. |
| June | Succession plant lettuce and greens. Keep beds weeded and watered consistently. |
| July | Harvest regularly to encourage production. Monitor for pests and disease. |
| August | Midsummer: harvest beans, zucchini, cucumbers. Start brassica seeds indoors for fall. |
| September | First fall frost approaching (around October 20). Transplant fall brassicas. Sow spinach, arugula, and radishes. |
| October | First frost around October 20. Harvest tomatoes and peppers before frost. Cover cold-hardy crops with row covers to extend the season. |
| November | Harvest remaining cold-hardy crops: kale, carrots, and beets. Plant garlic bulbs for next year. |
| December | Clean up spent plants. Add compost to beds. Rest, review, and plan next year's garden. |
What grows in a 184-day season
Frequently Asked Questions
What is the last frost date for Sumner, WA (ZIP 98390)?
The median last spring frost date for Sumner, WA (ZIP code 98390) is around April 19. This is the 50th-percentile date — meaning half of all years see frost end before this date. Use the 10% and 90% dates to understand the full range of risk in your area.
What is the first fall frost date in Sumner, WA?
The median first fall frost date for Sumner, WA is around October 20. Plan to harvest or protect frost-sensitive crops like tomatoes and peppers at least a week before this date to avoid losses.
How long is the growing season in Sumner, WA?
The frost-free growing season in Sumner is about 184 days. This window — from your last spring frost to your first fall frost — is when warm-season vegetables thrive. Cold-hardy crops like kale, spinach, and peas can extend your season by weeks on either side.
What USDA hardiness zone is Sumner, WA?
Based on frost date patterns, Sumner falls approximately in 8b. USDA hardiness zones are determined by average annual minimum winter temperatures and guide both plant selection and planting timing for your location.
When should I start tomatoes indoors in Sumner, WA?
Start tomato seeds indoors 6–8 weeks before your last frost date (around April 19). For Sumner, that's roughly February 23 to March 8. Transplant outdoors 1–2 weeks after your last frost.
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