Rail Road Flat, CA planting calendar
- USDA zone
- 9a20 to 25 °F
- Last frost
- May 7avg, 32°F
- First frost
- Oct 28avg, 32°F
- Growing season
- 169days
Rail Road Flat, California is in USDA plant hardiness zone 9a. Its average last spring frost is around May 7 and the first fall frost around October 28, giving a growing season of about 169 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.
Rail Road Flat planting calendar
Each crop's windows are counted from Rail Road Flat'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 12 – Mar 26 | May 14 – May 21 | Jul 13 – Aug 2 | — |
| Pepper | Very tender | Feb 26 – Mar 12 | May 21 – May 28 | Jul 20 – Aug 19 | — |
| Cucumber | Tender | Apr 9 – Apr 16 | May 14 – May 21 | Jul 3 – Jul 23 | — |
| Summer squash / zucchini | Tender | — | May 14 – May 21 | Jun 28 – Jul 13 | — |
| Bush bean | Tender | — | May 14 – May 21 | Jul 3 – Jul 13 | Aug 29 – Sep 8 |
| Sweet corn | Tender | — | May 7 – May 21 | Jul 6 – Aug 5 | — |
| Basil | Very tender | Mar 26 – Apr 9 | May 14 – May 21 | Jun 13 – Jun 28 | — |
| Lettuce | Half-hardy | Mar 26 – Apr 9 | Apr 9 – Apr 23 | May 24 – Jun 8 | Aug 15 – Aug 30 |
| Pea | Hardy | — | Mar 26 – Apr 9 | May 20 – Jun 4 | Aug 5 – Aug 20 |
| Spinach | Hardy | — | Mar 26 – Apr 9 | May 5 – May 15 | Aug 25 – Sep 4 |
| Carrot | Half-hardy | — | Apr 16 – Apr 23 | Jun 15 – Jul 5 | Jul 26 – Aug 15 |
| Broccoli | Half-hardy | Mar 12 – Mar 26 | Apr 9 – Apr 23 | Jun 3 – Jun 23 | Jul 31 – Aug 20 |
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 USC00041277. 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 | May 30 | Jun 14 | Oct 11 | Nov 1 | 136 |
| 32°F (freeze) | May 7 | May 31 | Oct 28 | Nov 16 | 169 |
| 28°F | Apr 18 | May 12 | Nov 14 | Dec 5 | 207 |
| 24°F | Mar 27 | Apr 20 | Dec 3 | Dec 23 | 249 |
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) | 2,183 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 4,366 | cool-season crops (brassicas, greens) |
Hardiness zone 9a
Rail Road Flat 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 Rail Road Flat?
- Rail Road Flat, California 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 Rail Road Flat?
- The average (median) last spring frost at 32°F is around May 7, from NOAA's 1991–2020 climate normals at the nearest reporting station. Roughly one year in ten the last frost is as late as May 31, so wait until then before setting out frost-tender plants if you want to be safe.
- When is the first fall frost in Rail Road Flat?
- The average first fall frost at 32°F is around October 28. That leaves a growing season of about 169 days between the average last spring and first fall frosts.
- When should I start tomatoes in Rail Road Flat?
- Start tomato seeds indoors about Mar 12 – Mar 26 and transplant them outside about May 14 – May 21, once the danger of frost has passed. Estimated first harvest is around Jul 13 – Aug 2.
- How long is the growing season in Rail Road Flat?
- About 169 days at the 32°F threshold (NOAA 1991–2020, median) — the span between the average last spring frost (~May 7) and the average first fall frost (~October 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 USC00041277 (Calaveras Big Trees, 13.8 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.