Renton, Washington: planting zone & frost dates
Renton is in USDA plant hardiness zone 9a, where the average coldest winter night reaches 20 to 25°F (-6.7 to -3.9°C). The typical last spring frost is around Mar 22 and the first fall frost around Nov 7.
Frost dates
| Probability | Last spring frost (32°F) | First fall frost (32°F) |
|---|---|---|
| Safer (10% risk) | Mar 31 | Oct 29 |
| Typical planning date (30% risk) | Mar 22 | Nov 7 |
| Median (50%) | Mar 13 | Nov 16 |
How to read this: after the spring "10% risk" date, a 32°F frost happens in only about 1 year in 10. In fall, the "10% risk" date is the early end — a frost before it happens about 1 year in 10.
Frost data comes from NOAA station RENTON MUNI AP, WA (USW00094248), 1.4 mi (2.2 km) from the city center and 46 ft lower than the city center (-14 m). Record used for the 1991–2020 normals: 19 years.
Why your yard may differ from the station: microclimates.
Hardiness zone across Renton
Renton spans more than one half-zone. Share of the city's land area by zone (via its 5 ZIP codes): 9a (68%), 8b (32%). The headline zone is the one covering the most land. Look up your ZIP for your exact zone.
Vegetable planting calendar for Renton
Dates are counted from the 30%-risk frost dates above (last frost Mar 22, first frost Nov 7). Shift a week later in cold spots or low-lying ground.
| Crop | Start indoors | Transplant / plant out | Direct sow | Fall crop sow/plant |
|---|---|---|---|---|
| Tomato | Jan 25 – Feb 8 | Mar 29 – Apr 12 | — | — |
| Pepper | Jan 11 – Jan 25 | Apr 5 – Apr 19 | — | — |
| Lettuce | Feb 8 – Feb 22 | Mar 8 – Mar 29 | Feb 22 – Apr 5 | Aug 29 – Sep 26 |
| Green Beans | — | — | Mar 29 – May 3 | Aug 15 – Aug 29 |
| Sweet Corn | — | — | Mar 29 – Apr 26 | — |
| Zucchini & Summer Squash | Feb 22 – Mar 1 | Mar 29 – Apr 12 | Mar 29 – Apr 19 | Aug 15 – Aug 29 |
| Cucumber | Feb 22 – Mar 1 | Apr 5 – Apr 12 | Mar 29 – Apr 19 | Aug 15 – Aug 29 |
| Carrot | — | — | Mar 1 – Apr 5 | Aug 15 – Aug 29 |
| Onion | Dec 28 – Jan 11 | Feb 22 – Mar 8 | — | — |
| Potato | — | Feb 22 – Mar 15 | — | — |
| Basil | Feb 8 – Feb 22 | Apr 5 – Apr 19 | Apr 5 – Apr 26 | — |
| Spinach | — | — | Feb 8 – Mar 8 | Sep 12 – Oct 10 |
| Kale | Jan 25 – Feb 8 | Feb 22 – Mar 15 | Feb 22 – Mar 15 | Aug 29 – Sep 26 |
| Broccoli | Jan 25 – Feb 8 | Mar 8 – Mar 29 | — | Aug 15 – Aug 29 |
| Peas | — | — | Feb 8 – Mar 1 | Aug 29 – Sep 12 |
| Eggplant | Jan 11 – Jan 25 | Apr 5 – Apr 19 | — | — |
| Cabbage | Jan 25 – Feb 8 | Feb 22 – Mar 8 | — | Aug 15 – Aug 29 |
| Radish | — | — | Feb 15 – Apr 5 | Sep 26 – Oct 24 |
| Strawberry | — | Feb 22 – Mar 15 | — | — |
| Beets | — | — | Mar 1 – Apr 12 | Aug 29 – Sep 12 |
Nearby cities in Washington
- Kent — zone 8b, last frost Mar 29, first frost Nov 3
- Bellevue — zone 8b, last frost Mar 16, first frost Nov 15
- Auburn — zone 8b, last frost Mar 29, first frost Nov 3
- Seattle — zone 9a, last frost Mar 16, first frost Nov 15
- Redmond — zone 8b, last frost Mar 16, first frost Nov 15
- Kirkland — zone 9a, last frost Mar 16, first frost Nov 15
More: all Washington cities · other zone 9a cities: San Antonio, TX, Austin, TX, Seattle, WA, Las Vegas, NV, Portland, OR, Tucson, AZ, Baton Rouge, LA, Tallahassee, FL
Renton gardening questions
When is the last frost in Renton, WA?
Plan around Mar 22. At NOAA's Renton Municipal Airport, WA station, 1.4 mi from the city center, there is a 30% chance of a 32°F frost after that date. Half of springs have their last frost by Mar 13, and after Mar 31 the risk drops to about 1 in 10. A hard freeze (28°F) usually ends earlier, around Feb 13. The 90% and 10% dates are 40 days apart, close to the 36-day median for cities on this site.
When should I plant tomatoes in Renton, WA?
Start seeds indoors Jan 25 – Feb 8 and set transplants outside Mar 29 – Apr 12, once nights stay above 50°F and the soil is near 60°F. That leaves 230 days between the 30% frost dates, enough for most varieties including 80–85-day slicers. More: tomato planting dates by zone.
How long is the growing season in Renton?
About 248 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 221 days, and in 1 year in 10 it runs 280 days or more. In fall there is a 10% chance of frost by Oct 29 and a 30% chance by Nov 7. That ranks 7th longest of 18 Washington cities on this site.
When should I plant a fall garden in Renton?
Count back from the first fall frost (Nov 7): transplant broccoli Aug 15 – Aug 29; sow kale Aug 29 – Sep 26; sow lettuce Aug 29 – Sep 26; sow radishes Sep 26 – Oct 24. Hardy crops keep growing through light frosts; the median 28°F hard freeze here is Dec 6. How the math works: succession and fall planting.
Did Renton's hardiness zone change on the 2023 map?
Yes. Most of Renton was zone 8b on the 2012 map and is zone 9a on the 2023 map — half a zone warmer, like about 56% of U.S. ZIP codes. The shift comes from a newer 1991–2020 averaging period plus more weather stations and better mapping; it does not mean last frost comes earlier. Why the 2023 map is warmer.
Is all of Renton in zone 9a?
No. Zone 9a covers about 68% of the city's land; the rest is in 8b (32%), measured across the city's 5 ZIP codes. Check your own ZIP code in the table above or with the ZIP lookup.