Kennewick, WA planting calendar
- USDA zone
- 7b5 to 10 °F
- Last frost
- Mar 28avg, 32°F
- First frost
- Oct 30avg, 32°F
- Growing season
- 216days
Kennewick, Washington is in USDA plant hardiness zone 7b. Its average last spring frost is around March 28 and the first fall frost around October 30, giving a growing season of about 216 days (NOAA 1991–2020 normals, 32°F, median). Start tender crops like tomatoes and peppers indoors weeks before the last frost and set them out afterward; sow hardy crops such as peas, spinach, and lettuce before it. The planner below turns those frost dates into a printable per-crop planting calendar.
Kennewick planting calendar
Each crop's windows are counted from Kennewick's average frost dates. hatched = start seeds indoors, solid green = plant out, teal = a fall sowing, and the terracotta dot marks the estimated first harvest. Ranges are extension-guide planning guidance, not guarantees.
- Start indoors
- Plant out
- Fall sowing
- First harvest
| Crop | Frost tolerance | Start indoors | Plant out | First harvest | Fall planting |
|---|---|---|---|---|---|
| Tomato | Tender | Jan 31 – Feb 14 | Apr 4 – Apr 11 | Jun 3 – Jun 23 | — |
| Pepper | Very tender | Jan 17 – Jan 31 | Apr 11 – Apr 18 | Jun 10 – Jul 10 | — |
| Cucumber | Tender | Feb 28 – Mar 7 | Apr 4 – Apr 11 | May 24 – Jun 13 | — |
| Summer squash / zucchini | Tender | — | Apr 4 – Apr 11 | May 19 – Jun 3 | — |
| Bush bean | Tender | — | Apr 4 – Apr 11 | May 24 – Jun 3 | Aug 31 – Sep 10 |
| Sweet corn | Tender | — | Mar 28 – Apr 11 | May 27 – Jun 26 | — |
| Basil | Very tender | Feb 14 – Feb 28 | Apr 4 – Apr 11 | May 4 – May 19 | — |
| Lettuce | Half-hardy | Feb 14 – Feb 28 | Feb 28 – Mar 14 | Apr 14 – Apr 29 | Aug 17 – Sep 1 |
| Pea | Hardy | — | Feb 14 – Feb 28 | Apr 10 – Apr 25 | Aug 7 – Aug 22 |
| Spinach | Hardy | — | Feb 14 – Feb 28 | Mar 26 – Apr 5 | Aug 27 – Sep 6 |
| Carrot | Half-hardy | — | Mar 7 – Mar 14 | May 6 – May 26 | Jul 28 – Aug 17 |
| Broccoli | Half-hardy | Jan 31 – Feb 14 | Feb 28 – Mar 14 | Apr 24 – May 14 | Aug 2 – Aug 22 |
Data: NOAA NCEI U.S. Climate Normals 1991–2020 (public domain) and USDA Plant Hardiness Zone Map 2023. Planting windows synthesized from U.S. Cooperative Extension guides.
Frost & freeze dates
From NOAA's 1991–2020 Climate Normals at station USC00454154. The median (p50) is the average date; the 90%-safe column is the date the freeze has passed in about 9 years out of 10 (p10 for spring, p90 for fall) — the conservative date to plant after or harvest before.
| Threshold | Last spring — avg | Last spring — 90%-safe | First fall — avg | First fall — 90%-safe | Season (days) |
|---|---|---|---|---|---|
| 36°F | Apr 14 | Apr 30 | Oct 21 | Nov 2 | 189 |
| 32°F (freeze) | Mar 28 | Apr 10 | Oct 30 | Nov 15 | 216 |
| 28°F | Mar 8 | Mar 29 | Nov 11 | Dec 1 | 246 |
| 24°F | Feb 23 | Mar 12 | Nov 25 | Dec 20 | 277 |
32°F is the standard "freeze" line that damages tender crops; lighter 36°F frost can nip the most cold-sensitive plants, while hardy crops shrug off light frost down toward 28°F. Use the threshold that matches what you are protecting.
Growing degree days
Growing degree days (GDD) accumulate warmth above a base temperature over the year — a better predictor of crop development than the calendar alone. Warm-season crops need a long, warm GDD total; a short, cool GDD total favors greens and brassicas.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 3,502 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 6,075 | cool-season crops (brassicas, greens) |
Hardiness zone 7b
Kennewick sits in USDA plant hardiness zone 7b on the 2023 map — meaning its average annual extreme minimum winter temperature is about 5 to 10 °F. That number tells you which perennials, shrubs, and trees reliably survive an average winter here; it does not set your planting dates, which come from the frost calendar above.
Explore more places in zone 7b, or see all USDA hardiness zones.
Frequently asked questions
- What USDA hardiness zone is Kennewick?
- Kennewick, Washington is in USDA plant hardiness zone 7b on the 2023 map (average annual extreme minimum temperature 5 to 10 °F) — from the USDA Plant Hardiness Zone Map 2023, matched to this location's ZIP. See the methodology page for sources.
- When is the last frost in Kennewick?
- The average (median) last spring frost at 32°F is around March 28, from NOAA's 1991–2020 climate normals at the nearest reporting station. Roughly one year in ten the last frost is as late as April 10, so wait until then before setting out frost-tender plants if you want to be safe.
- When is the first fall frost in Kennewick?
- The average first fall frost at 32°F is around October 30. That leaves a growing season of about 216 days between the average last spring and first fall frosts.
- When should I start tomatoes in Kennewick?
- Start tomato seeds indoors about Jan 31 – Feb 14 and transplant them outside about Apr 4 – Apr 11, once the danger of frost has passed. Estimated first harvest is around Jun 3 – Jun 23.
- How long is the growing season in Kennewick?
- About 216 days at the 32°F threshold (NOAA 1991–2020, median) — the span between the average last spring frost (~March 28) and the average first fall frost (~October 30). Cold-hardy crops extend usable time at both ends; frost-tender crops fit inside it.
Sources & method
Frost, freeze, growing-season, and growing-degree-day figures are NOAA NCEI U.S. Climate Normals 1991–2020 for station USC00454154 (Kennewick, 5.8 km away). The hardiness zone is the USDA Plant Hardiness Zone Map 2023, matched to this location's ZIP. Planting windows are computed by counting from the average last and first frost using per-crop offsets synthesized from U.S. Cooperative Extension guides — the full method and citations are on the methodology page.