Kennewick, Washington: planting zone & frost dates
Kennewick is in USDA plant hardiness zone 7b, where the average coldest winter night reaches 5 to 10°F (-15.0 to -12.2°C). The typical last spring frost is around Apr 2 and the first fall frost around Oct 25.
Frost dates
| Probability | Last spring frost (32°F) | First fall frost (32°F) |
|---|---|---|
| Safer (10% risk) | Apr 10 | Oct 18 |
| Typical planning date (30% risk) | Apr 2 | Oct 25 |
| Median (50%) | Mar 28 | Oct 30 |
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 KENNEWICK, WA (USC00454154), 3.7 mi (5.9 km) from the city center and 164 ft lower than the city center (-50 m). Record used for the 1991–2020 normals: 27 years.
Why your yard may differ from the station: microclimates.
Hardiness zone across Kennewick
All 3 ZIP codes covering Kennewick are in zone 7b.
Vegetable planting calendar for Kennewick
Dates are counted from the 30%-risk frost dates above (last frost Apr 2, first frost Oct 25). Shift a week later in cold spots or low-lying ground.
| Crop | Start indoors | Transplant / plant out | Direct sow | Fall crop sow/plant |
|---|---|---|---|---|
| Tomato | Feb 5 – Feb 19 | Apr 9 – Apr 23 | — | — |
| Pepper | Jan 22 – Feb 5 | Apr 16 – Apr 30 | — | — |
| Lettuce | Feb 19 – Mar 5 | Mar 19 – Apr 9 | Mar 5 – Apr 16 | Aug 16 – Sep 13 |
| Green Beans | — | — | Apr 9 – May 14 | Aug 2 – Aug 16 |
| Sweet Corn | — | — | Apr 9 – May 7 | — |
| Zucchini & Summer Squash | Mar 5 – Mar 12 | Apr 9 – Apr 23 | Apr 9 – Apr 30 | Aug 2 – Aug 16 |
| Cucumber | Mar 5 – Mar 12 | Apr 16 – Apr 23 | Apr 9 – Apr 30 | Aug 2 – Aug 16 |
| Carrot | — | — | Mar 12 – Apr 16 | Aug 2 – Aug 16 |
| Onion | Jan 8 – Jan 22 | Mar 5 – Mar 19 | — | — |
| Potato | — | Mar 5 – Mar 26 | — | — |
| Basil | Feb 19 – Mar 5 | Apr 16 – Apr 30 | Apr 16 – May 7 | — |
| Spinach | — | — | Feb 19 – Mar 19 | Aug 30 – Sep 27 |
| Kale | Feb 5 – Feb 19 | Mar 5 – Mar 26 | Mar 5 – Mar 26 | Aug 16 – Sep 13 |
| Broccoli | Feb 5 – Feb 19 | Mar 19 – Apr 9 | — | Aug 2 – Aug 16 |
| Peas | — | — | Feb 19 – Mar 12 | Aug 16 – Aug 30 |
| Eggplant | Jan 22 – Feb 5 | Apr 16 – Apr 30 | — | — |
| Cabbage | Feb 5 – Feb 19 | Mar 5 – Mar 19 | — | Aug 2 – Aug 16 |
| Radish | — | — | Feb 26 – Apr 16 | Sep 13 – Oct 11 |
| Strawberry | — | Mar 5 – Mar 26 | — | — |
| Beets | — | — | Mar 12 – Apr 23 | Aug 16 – Aug 30 |
Nearby cities in Washington
- Pasco — zone 7a, last frost May 2, first frost Oct 4
- Yakima — zone 7a, last frost Apr 18, first frost Oct 17
- Spokane — zone 6b, last frost May 1, first frost Oct 7
- Spokane Valley — zone 7a, last frost May 1, first frost Oct 7
- Auburn — zone 8b, last frost Mar 29, first frost Nov 3
- Kent — zone 8b, last frost Mar 29, first frost Nov 3
More: all Washington cities · other zone 7b cities: New York, NY, Philadelphia, PA, Oklahoma City, OK, Nashville, TN, Washington, DC, Baltimore, MD, Albuquerque, NM, Tulsa, OK
Kennewick gardening questions
When is the last frost in Kennewick, WA?
Plan around Apr 2. At NOAA's Kennewick, WA station, 3.7 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 28, and after Apr 10 the risk drops to about 1 in 10. A hard freeze (28°F) usually ends earlier, around Mar 8. The 90% and 10% dates are 32 days apart, close to the 36-day median for cities on this site.
When should I plant tomatoes in Kennewick, WA?
Start seeds indoors Feb 5 – Feb 19 and set transplants outside Apr 9 – Apr 23, once nights stay above 50°F and the soil is near 60°F. That leaves 206 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 Kennewick?
About 216 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 196 days, and in 1 year in 10 it runs 239 days or more. In fall there is a 10% chance of frost by Oct 18 and a 30% chance by Oct 25. That ranks 13th longest of 18 Washington cities on this site.
When should I plant a fall garden in Kennewick?
Count back from the first fall frost (Oct 25): transplant broccoli Aug 2 – Aug 16; sow kale Aug 16 – Sep 13; sow lettuce Aug 16 – Sep 13; sow radishes Sep 13 – Oct 11. Hardy crops keep growing through light frosts; the median 28°F hard freeze here is Nov 11. How the math works: succession and fall planting.
Did Kennewick's hardiness zone change on the 2023 map?
Yes. Most of Kennewick was zone 7a on the 2012 map and is zone 7b 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.
How does Kennewick compare with Pasco, WA?
Kennewick is zone 7b and Pasco is zone 7a. The typical last spring frost in Kennewick (Apr 2) comes about 30 days earlier than in Pasco, WA (May 2), 5 miles away, and the first fall frost is Oct 25 versus Oct 4. Kennewick sits about 156 ft higher, which explains part of the gap. The two cities use different NOAA stations.