Grenora, ND 59247 planting calendar
- USDA zone
- 3b−35 to −30 °F
- Last frost
- May 16avg, 32°F
- First frost
- Sep 18avg, 32°F
- Growing season
- 125days
Grenora, North Dakota is in USDA plant hardiness zone 3b. Its average last spring frost is around May 16 and the first fall frost around September 18, giving a growing season of about 125 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.
Grenora planting calendar
Each crop's windows are counted from Grenora'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 20 – Jul 30 |
| 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 6 – Jul 21 |
| Pea | Hardy | — | Apr 4 – Apr 18 | May 29 – Jun 13 | Jun 26 – Jul 11 |
| Spinach | Hardy | — | Apr 4 – Apr 18 | May 14 – May 24 | Jul 16 – Jul 26 |
| Carrot | Half-hardy | — | Apr 25 – May 2 | Jun 24 – Jul 14 | Jun 16 – Jul 6 |
| Broccoli | Half-hardy | Mar 21 – Apr 4 | Apr 18 – May 2 | Jun 12 – Jul 2 | Jun 21 – Jul 11 |
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 USC00245572. 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 29 | Jun 23 | Sep 10 | Sep 21 | 103 |
| 32°F (freeze) | May 16 | May 30 | Sep 18 | Sep 28 | 125 |
| 28°F | May 5 | May 17 | Sep 25 | Oct 6 | 141 |
| 24°F | Apr 27 | May 9 | Oct 3 | Oct 18 | 160 |
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) | 2,037 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 3,778 | cool-season crops (brassicas, greens) |
Hardiness zone 3b
Grenora sits in USDA plant hardiness zone 3b on the 2023 map — meaning its average annual extreme minimum winter temperature is about −35 to −30 °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 3b, or see all USDA hardiness zones.
Frequently asked questions
- What USDA hardiness zone is Grenora?
- Grenora, North Dakota is in USDA plant hardiness zone 3b on the 2023 map (average annual extreme minimum temperature −35 to −30 °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 Grenora?
- 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 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 Grenora?
- The average first fall frost at 32°F is around September 18. That leaves a growing season of about 125 days between the average last spring and first fall frosts.
- When should I start tomatoes in Grenora?
- 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 Grenora?
- About 125 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 18). 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 USC00245572 (Medicine Lake 3 Se, 6.5 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.