Fall in zone 4aPhoto: Dietmar Rabich, CC BY-SA 4.0, via Wikimedia Commons
Frost dates for ZIP 58631 (Glen Ullin, ND)
Average last spring and first fall frost dates with 10%, 50% and 90% odds, from NOAA's 1991–2020 climate normals for the nearest weather station, Hebron, ND (12 miles away).
- Average last spring frostMay 1950% chance of a 32°F freeze after this date
- Average first fall frostSep 2150% chance of a 32°F freeze by this date
- Growing season (frost-free)123 daysmedian, 32°F threshold
- USDA hardiness zone4a-30 to -25°F avg. coldest night
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This week in your yard
As of Oct 18, 2026, from your frost dates, zone and soil temperature. Lawn timing · Vegetables · Pruning · Plants
Soil temperature now
2-inch depth
49°F Below 50°F
24-hour average · latest 50°F, as of Oct 18, 2:00 AM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Mandan #1 (44 mi).
4-inch depth
49°F Below 50°F
24-hour average · latest 49°F, as of Oct 18, 2:00 AM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Mandan #1 (44 mi).
Fall: Texas A&M AgriLife times fall pre-emergent (for winter weeds such as annual bluegrass) to soil cooling to about 70°F for several days. The 50–55°F band is the spring trigger. Always read and follow the product label.
7-day forecast and frost risk
The latest National Weather Service 7-day forecast and any Frost Advisory or Freeze Warning for 58631 load here. You can also open the NWS forecast for this ZIP.
Pre-emergent
Soil is 49°F at 4 inches (estimated soil temperature, not a station reading). Fall pre-emergent window is mostly past. Next: spring, when soil reaches 50°F (typically mid-April to early May).
Fertilizer window
Lawn region: North (cool-season). Timing only; always follow the product label.
- Kentucky bluegrass (cool-season): Early fall: Around Labor Day (late August–September); Late fall: Late October–November, before the ground freezes; Late spring: Optional around Memorial Day. Avoid: Early-spring and midsummer feeding (pushes top growth, favors crabgrass).
Plant now
No vegetable planting windows are open this week.
Prune now
No frost-timed pruning windows are open this week.
Spring-flowering shrubs are pruned right after their flowers fade, not by date. See the pruning guide.
Last spring frost odds
| Chance of a 32°F freeze after this date | Date |
|---|---|
| 90% (early: most years still freeze after this) | May 7 |
| 50% (the "average" last frost) | May 19 |
| 10% (cautious: only 1 year in 10 freezes later) | Jun 2 |
Most gardeners plant frost-tender crops (tomatoes, peppers, basil) after the 50% date, and closer to the 10% date for less risk.
First fall frost odds
| Chance the first 32°F freeze has happened by this date | Date |
|---|---|
| 10% (early: 1 year in 10 freezes this soon) | Sep 7 |
| 50% (the "average" first frost) | Sep 21 |
| 90% (late: most years have frozen by now) | Oct 4 |
Light frost, freeze and hard freeze
| Threshold | Last spring (50%) | First fall (50%) |
|---|---|---|
| 36°F (light frost possible on clear, calm nights) | May 31 | Sep 10 |
| 32°F (freeze) | May 19 | Sep 21 |
| 28°F (hard freeze) | May 10 | Sep 30 |
n/a means NOAA did not publish a date at that threshold for this station (usually because it rarely gets that cold).
Vegetable planting calendar for 58631
Dates count from your average last spring frost (May 19) and first fall frost (Sep 21). Half of years have a frost after the spring date, so give tender crops (tomatoes, peppers, squash) some slack.
| Crop | Start indoors | Spring planting | Fall planting |
|---|---|---|---|
| Tomato | Mar 24–Apr 7 | May 26–Jun 9 (transplant) | – |
| Pepper (sweet and hot) | Mar 10–24 | Jun 2–16 (transplant) | – |
| Eggplant | Mar 10–24 | Jun 2–16 (transplant) | – |
| Tomatillo | Mar 24–Apr 7 | May 26–Jun 9 (transplant) | – |
| Lettuce | Mar 24–Apr 7 | Apr 28–May 19 (transplant) Apr 21–Jun 2 (sow outdoors) | Jul 27–Aug 17 (transplant) Jul 13–Aug 10 (sowing) |
| Spinach | – | Apr 7–28 (sow outdoors) | Jul 27–Aug 17 (sowing) |
| Kale | Mar 24–Apr 7 | Apr 21–May 5 (transplant) Apr 21–May 5 (sow outdoors) | Jun 29–Jul 27 (transplant) Jun 15–Jul 13 (sowing) |
| Collards | Mar 24–Apr 7 | Apr 21–May 19 (transplant) Apr 21–May 19 (sow outdoors) | Jun 29–Jul 27 (transplant) Jun 15–Jul 13 (sowing) |
| Broccoli | Mar 10–24 | Apr 21–May 5 (transplant) | Jun 15–Jul 13 (transplant) |
| Cabbage | Mar 10–24 | Apr 21–May 5 (transplant) | Jun 15–Jul 13 (transplant) |
| Cauliflower | Mar 10–24 | May 5–19 (transplant) | Jun 15–Jul 13 (transplant) |
| Brussels sprouts | Feb 24–Mar 10 | Apr 21–May 5 (transplant) | Jun 1–22 (transplant) |
| Kohlrabi | Mar 24–Apr 7 | Apr 21–May 5 (transplant) Apr 21–May 5 (sow outdoors) | Jul 13–27 (sowing) |
| Bok choy / Asian greens | – | Apr 21–May 5 (sow outdoors) | Jul 27–Aug 10 (sowing) |
| Arugula | – | Apr 21–May 19 (sow outdoors) | Jul 27–Aug 24 (sowing) |
| Mustard greens | – | Apr 21–May 12 (sow outdoors) | Jul 27–Aug 10 (sowing) |
| Swiss chard | Apr 7–21 | May 5–26 (transplant) May 5–Jun 2 (sow outdoors) | Jul 13–27 (sowing) |
| Beet | – | Apr 21–May 19 (sow outdoors) | Jul 13–27 (sowing) |
| Carrot | – | Apr 28–May 26 (sow outdoors) | Jun 29–Jul 13 (sowing) |
| Radish | – | Apr 14–May 26 (sow outdoors) | Aug 10–24 (sowing) |
| Turnip | – | Apr 21–May 12 (sow outdoors) | Jul 13–27 (sowing) |
| Parsnip | – | Apr 28–May 19 (sow outdoors) | – |
| Pea (garden, snap, snow) | – | Mar 24–Apr 21 (sow outdoors) | Jun 29–Jul 13 (sowing) |
| Onion (bulbing) | Feb 24–Mar 10 | Apr 7–21 (transplant) | – |
| Green onion / scallion | – | Apr 7–May 5 (sow outdoors) | Jul 13–27 (sowing) |
| Leek | Feb 24–Mar 10 | Apr 21–May 5 (transplant) | – |
| Garlic | – | – | Aug 10–Sep 7 (sowing) |
| Shallot | – | Apr 7–21 (transplant) | Aug 10–Sep 7 (sowing) |
| Potato | – | Apr 21–May 5 (transplant) | Jun 1–15 (transplant) |
| Sweet potato | – | Jun 9–23 (transplant) | – |
| Sweet corn | – | May 26–Jun 9 (sow outdoors) | – |
| Bean, bush (snap) | – | May 26–Jun 9 (sow outdoors) | – |
| Bean, pole | – | May 26–Jun 9 (sow outdoors) | – |
| Lima bean | – | Jun 2–16 (sow outdoors) | – |
| Southern pea (cowpea, black-eyed pea) | – | Jun 9–30 (sow outdoors) | – |
| Cucumber | Apr 21–28 | May 26–Jun 9 (transplant) May 26–Jun 9 (sow outdoors) | – |
| Summer squash / zucchini | Apr 21–28 | May 26–Jun 9 (transplant) May 26–Jun 9 (sow outdoors) | – |
| Winter squash | Apr 21–28 | May 26–Jun 9 (transplant) May 26–Jun 9 (sow outdoors) | – |
| Pumpkin | – | May 26–Jun 9 (sow outdoors) | – |
| Watermelon | Apr 21–28 | Jun 2–16 (transplant) Jun 2–16 (sow outdoors) | – |
| Cantaloupe / muskmelon | Apr 21–28 | Jun 2–16 (transplant) Jun 2–16 (sow outdoors) | – |
| Okra | Apr 7–21 | Jun 2–16 (transplant) Jun 2–16 (sow outdoors) | – |
| Celery | Feb 24–Mar 10 | May 26–Jun 2 (transplant) | – |
| Basil | Apr 7–21 | May 26–Jun 9 (transplant) May 26–Jun 9 (sow outdoors) | – |
| Cilantro | – | May 5–Jun 2 (sow outdoors) | Jul 27–Aug 10 (sowing) |
| Parsley | Mar 10–24 | May 5–19 (transplant) Apr 28–May 19 (sow outdoors) | – |
| Dill | – | May 19–Jun 2 (sow outdoors) | Jul 27–Aug 10 (sowing) |
| Sunflower | – | May 19–Jun 2 (sow outdoors) | – |
| Asparagus (crowns) | – | Apr 21–May 5 (transplant) | – |
| Rhubarb (crowns) | – | Apr 21–May 5 (transplant) | – |
| Strawberry (plants) | – | Apr 21–May 5 (transplant) | Jul 13–Aug 10 (transplant) |
Typical ranges from university extension planting calendars, adjusted to your frost dates. Probabilities, not guarantees. Fall windows that would overlap spring planting are left out, as are fall crops of frost-tender plants where the frost-free season is under 210 days.
Where these numbers come from
Station: Hebron, ND (NOAA GHCN-Daily ID USC00324102), elevation 2,160 ft, 12.1 miles from the ZIP's center point. NOAA completeness flag: S (standard, 24+ years).
Nearby stations
| Station | Distance | Last frost (50%) | First frost (50%) |
|---|---|---|---|
| Heart Butte Dam, ND | 14 mi | May 14 | Sep 29 |
| Almont, ND | 17 mi | May 17 | Sep 21 |
| New Salem 5NW, ND | 18 mi | May 18 | Sep 24 |
The average last-frost dates of these stations span 5 days, a rough guide to local variation. See data sources & methods.
Frost questions for 58631
When is the last frost in 58631?
The average (50% chance) last spring freeze of 32°F for ZIP 58631 is May 19. For a more cautious planting date, use June 2, when only 1 year in 10 still sees a later freeze.
When is the first frost in 58631?
The average first fall freeze is September 21. In 1 year in 10 it comes by September 7.
What hardiness zone is 58631?
ZIP 58631 is in USDA zone 4a (-30 to -25°F average coldest winter night), per the 2023 USDA Plant Hardiness Zone Map ZIP listing.
What is the soil temperature in 58631 right now?
This page shows the latest 2-inch and 4-inch soil temperature from the nearest public soil station (USDA SCAN, NOAA USCRN or TexMesonet), or a labeled estimate when no station is close, against the 50–55°F spring pre-emergent band.
Nearby ZIP codes
58638 Hebron 58520 Almont 58563 New Salem 58652 Richardton 58533 Elgin 58562 New Leipzig 58656 Taylor 58641
Other ZIP codes in Morton County
58520 58535 58554 58563 58566 58570 58638 All Morton County frost dates · North Dakota frost dates
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Weekly yard timing, plus frost and soil-temperature alerts for your ZIP code.
- Freeze alerts
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Free. One weekly email plus alerts when your ZIP has a frost or a soil-temperature change worth acting on. After you submit, Kit (our email provider) sends a confirmation email: check your email and click the link to confirm. You aren't subscribed until you do. We collect only your email address and ZIP, sent to Kit to deliver The Dial. Unsubscribe anytime.