Oxford, ID 83228 planting calendar
- USDA zone
- 6b−5 to 0 °F
- Last frost
- May 16avg, 32°F
- First frost
- Sep 28avg, 32°F
- Growing season
- 133days
Oxford, Idaho is in USDA plant hardiness zone 6b. Its average last spring frost is around May 16 and the first fall frost around September 28, giving a growing season of about 133 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.
Oxford planting calendar
Each crop's windows are counted from Oxford'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 | Mar 21 – Apr 4 | May 23 – May 30 | Jul 22 – Aug 11 | — |
| Pepper | Very tender | Mar 7 – Mar 21 | May 30 – Jun 6 | Jul 29 – Aug 28 | — |
| Cucumber | Tender | Apr 18 – Apr 25 | May 23 – May 30 | Jul 12 – Aug 1 | — |
| Summer squash / zucchini | Tender | — | May 23 – May 30 | Jul 7 – Jul 22 | — |
| Bush bean | Tender | — | May 23 – May 30 | Jul 12 – Jul 22 | Jul 30 – Aug 9 |
| Sweet corn | Tender | — | May 16 – May 30 | Jul 15 – Aug 14 | — |
| Basil | Very tender | Apr 4 – Apr 18 | May 23 – May 30 | Jun 22 – Jul 7 | — |
| Lettuce | Half-hardy | Apr 4 – Apr 18 | Apr 18 – May 2 | Jun 2 – Jun 17 | Jul 16 – Jul 31 |
| Pea | Hardy | — | Apr 4 – Apr 18 | May 29 – Jun 13 | Jul 6 – Jul 21 |
| Spinach | Hardy | — | Apr 4 – Apr 18 | May 14 – May 24 | Jul 26 – Aug 5 |
| Carrot | Half-hardy | — | Apr 25 – May 2 | Jun 24 – Jul 14 | Jun 26 – Jul 16 |
| Broccoli | Half-hardy | Mar 21 – Apr 4 | Apr 18 – May 2 | Jun 12 – Jul 2 | Jul 1 – Jul 21 |
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 USC00107346. 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 | Jun 3 | Jun 19 | Sep 17 | Oct 1 | 102 |
| 32°F (freeze) | May 16 | Jun 4 | Sep 28 | Oct 14 | 133 |
| 28°F | Apr 30 | May 13 | Oct 10 | Oct 26 | 164 |
| 24°F | Apr 12 | Apr 29 | Oct 24 | Nov 8 | 195 |
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) | 2,280 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 4,253 | cool-season crops (brassicas, greens) |
Hardiness zone 6b
Oxford sits in USDA plant hardiness zone 6b on the 2023 map — meaning its average annual extreme minimum winter temperature is about −5 to 0 °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 6b, or see all USDA hardiness zones.
Frequently asked questions
- What USDA hardiness zone is Oxford?
- Oxford, Idaho is in USDA plant hardiness zone 6b on the 2023 map (average annual extreme minimum temperature −5 to 0 °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 Oxford?
- The average (median) last spring frost at 32°F is around May 16, from NOAA's 1991–2020 climate normals at the nearest reporting station. Roughly one year in ten the last frost is as late as June 4, so wait until then before setting out frost-tender plants if you want to be safe.
- When is the first fall frost in Oxford?
- The average first fall frost at 32°F is around September 28. That leaves a growing season of about 133 days between the average last spring and first fall frosts.
- When should I start tomatoes in Oxford?
- Start tomato seeds indoors about Mar 21 – Apr 4 and transplant them outside about May 23 – May 30, once the danger of frost has passed. Estimated first harvest is around Jul 22 – Aug 11.
- How long is the growing season in Oxford?
- About 133 days at the 32°F threshold (NOAA 1991–2020, median) — the span between the average last spring frost (~May 16) and the average first fall frost (~September 28). 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 USC00107346 (Preston, 21.4 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.