Lavina, MT planting calendar
- USDA zone
- 4b−25 to −20 °F
- Last frost
- May 17avg, 32°F
- First frost
- Sep 23avg, 32°F
- Growing season
- 127days
Lavina, Montana is in USDA plant hardiness zone 4b. Its average last spring frost is around May 17 and the first fall frost around September 23, giving a growing season of about 127 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.
Lavina planting calendar
Each crop's windows are counted from Lavina'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 22 – Apr 5 | May 24 – May 31 | Jul 23 – Aug 12 | — |
| Pepper | Very tender | Mar 8 – Mar 22 | May 31 – Jun 7 | Jul 30 – Aug 29 | — |
| Cucumber | Tender | Apr 19 – Apr 26 | May 24 – May 31 | Jul 13 – Aug 2 | — |
| Summer squash / zucchini | Tender | — | May 24 – May 31 | Jul 8 – Jul 23 | — |
| Bush bean | Tender | — | May 24 – May 31 | Jul 13 – Jul 23 | Jul 25 – Aug 4 |
| Sweet corn | Tender | — | May 17 – May 31 | Jul 16 – Aug 15 | — |
| Basil | Very tender | Apr 5 – Apr 19 | May 24 – May 31 | Jun 23 – Jul 8 | — |
| Lettuce | Half-hardy | Apr 5 – Apr 19 | Apr 19 – May 3 | Jun 3 – Jun 18 | Jul 11 – Jul 26 |
| Pea | Hardy | — | Apr 5 – Apr 19 | May 30 – Jun 14 | Jul 1 – Jul 16 |
| Spinach | Hardy | — | Apr 5 – Apr 19 | May 15 – May 25 | Jul 21 – Jul 31 |
| Carrot | Half-hardy | — | Apr 26 – May 3 | Jun 25 – Jul 15 | Jun 21 – Jul 11 |
| Broccoli | Half-hardy | Mar 22 – Apr 5 | Apr 19 – May 3 | Jun 13 – Jul 3 | Jun 26 – Jul 16 |
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 USC00247261. 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 | Sep 12 | Sep 26 | 104 |
| 32°F (freeze) | May 17 | May 30 | Sep 23 | Oct 6 | 127 |
| 28°F | May 5 | May 19 | Oct 3 | Oct 16 | 149 |
| 24°F | Apr 26 | May 9 | Oct 13 | Oct 27 | 169 |
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) | 2,102 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 4,062 | cool-season crops (brassicas, greens) |
Hardiness zone 4b
Lavina sits in USDA plant hardiness zone 4b on the 2023 map — meaning its average annual extreme minimum winter temperature is about −25 to −20 °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 4b, or see all USDA hardiness zones.
Frequently asked questions
- What USDA hardiness zone is Lavina?
- Lavina, Montana is in USDA plant hardiness zone 4b on the 2023 map (average annual extreme minimum temperature −25 to −20 °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 Lavina?
- The average (median) last spring frost at 32°F is around May 17, 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 30, so wait until then before setting out frost-tender plants if you want to be safe.
- When is the first fall frost in Lavina?
- The average first fall frost at 32°F is around September 23. That leaves a growing season of about 127 days between the average last spring and first fall frosts.
- When should I start tomatoes in Lavina?
- Start tomato seeds indoors about Mar 22 – Apr 5 and transplant them outside about May 24 – May 31, once the danger of frost has passed. Estimated first harvest is around Jul 23 – Aug 12.
- How long is the growing season in Lavina?
- About 127 days at the 32°F threshold (NOAA 1991–2020, median) — the span between the average last spring frost (~May 17) and the average first fall frost (~September 23). 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 USC00247261 (Ryegate, 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.