North Bonneville, WA planting calendar
- USDA zone
- 9a20 to 25 °F
- Last frost
- Mar 14avg, 32°F
- First frost
- Nov 27avg, 32°F
- Growing season
- 257days
North Bonneville, Washington is in USDA plant hardiness zone 9a. Its average last spring frost is around March 14 and the first fall frost around November 27, giving a growing season of about 257 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.
North Bonneville planting calendar
Each crop's windows are counted from North Bonneville'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 17 – Jan 31 | Mar 21 – Mar 28 | May 20 – Jun 9 | — |
| Pepper | Very tender | Jan 3 – Jan 17 | Mar 28 – Apr 4 | May 27 – Jun 26 | — |
| Cucumber | Tender | Feb 14 – Feb 21 | Mar 21 – Mar 28 | May 10 – May 30 | — |
| Summer squash / zucchini | Tender | — | Mar 21 – Mar 28 | May 5 – May 20 | — |
| Bush bean | Tender | — | Mar 21 – Mar 28 | May 10 – May 20 | Sep 28 – Oct 8 |
| Sweet corn | Tender | — | Mar 14 – Mar 28 | May 13 – Jun 12 | — |
| Basil | Very tender | Jan 31 – Feb 14 | Mar 21 – Mar 28 | Apr 20 – May 5 | — |
| Lettuce | Half-hardy | Jan 31 – Feb 14 | Feb 14 – Feb 28 | Mar 31 – Apr 15 | Sep 14 – Sep 29 |
| Pea | Hardy | — | Jan 31 – Feb 14 | Mar 27 – Apr 11 | Sep 4 – Sep 19 |
| Spinach | Hardy | — | Jan 31 – Feb 14 | Mar 12 – Mar 22 | Sep 24 – Oct 4 |
| Carrot | Half-hardy | — | Feb 21 – Feb 28 | Apr 22 – May 12 | Aug 25 – Sep 14 |
| Broccoli | Half-hardy | Jan 17 – Jan 31 | Feb 14 – Feb 28 | Apr 10 – Apr 30 | Aug 30 – Sep 19 |
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 USC00350897. 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 15 | May 5 | Nov 10 | Nov 27 | 207 |
| 32°F (freeze) | Mar 14 | Apr 4 | Nov 27 | Dec 15 | 257 |
| 28°F | Feb 14 | Mar 10 | Dec 14 | Jan 13 | 306 |
| 24°F | Jan 21 | Feb 26 | Dec 30 | Feb 10 | 342 |
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) | 2,407 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 4,963 | cool-season crops (brassicas, greens) |
Hardiness zone 9a
North Bonneville sits in USDA plant hardiness zone 9a on the 2023 map — meaning its average annual extreme minimum winter temperature is about 20 to 25 °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 9a, or see all USDA hardiness zones.
Frequently asked questions
- What USDA hardiness zone is North Bonneville?
- North Bonneville, Washington is in USDA plant hardiness zone 9a on the 2023 map (average annual extreme minimum temperature 20 to 25 °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 North Bonneville?
- The average (median) last spring frost at 32°F is around March 14, 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 4, so wait until then before setting out frost-tender plants if you want to be safe.
- When is the first fall frost in North Bonneville?
- The average first fall frost at 32°F is around November 27. That leaves a growing season of about 257 days between the average last spring and first fall frosts.
- When should I start tomatoes in North Bonneville?
- Start tomato seeds indoors about Jan 17 – Jan 31 and transplant them outside about Mar 21 – Mar 28, once the danger of frost has passed. Estimated first harvest is around May 20 – Jun 9.
- How long is the growing season in North Bonneville?
- About 257 days at the 32°F threshold (NOAA 1991–2020, median) — the span between the average last spring frost (~March 14) and the average first fall frost (~November 27). 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 USC00350897 (Bonneville Dam, 1.2 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.