Fall in zone 4aPhoto: Dietmar Rabich, CC BY-SA 4.0, via Wikimedia Commons
Frost dates for ZIP 59218 (Culbertson, MT)
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, Culbertson, MT (5 miles away).
- Average last spring frostMay 2150% chance of a 32°F freeze after this date
- Average first fall frostSep 2050% chance of a 32°F freeze by this date
- Growing season (frost-free)120 daysmedian, 32°F threshold
- USDA hardiness zone4a-30 to -25°F avg. coldest night
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Frost and freeze alerts from the NWS forecast for 59218, the spring soil-temperature heads-up for pre-emergent, and a short weekly yard-timing email.
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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
46°F Below 50°F
24-hour average · latest 48°F, as of Oct 18, 2:00 AM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Sidney (24 mi), Wolf Point 29 ENE (32 mi), Wolf Point 34 NE (44 mi).
4-inch depth
46°F Below 50°F
24-hour average · latest 48°F, as of Oct 18, 2:00 AM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Sidney (24 mi), Wolf Point 29 ENE (32 mi), Wolf Point 34 NE (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 59218 load here. You can also open the NWS forecast for this ZIP.
Pre-emergent
Soil is 46°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 mid-May).
Fertilizer window
Lawn region: Mountain West and High Plains. 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 8 |
| 50% (the "average" last frost) | May 21 |
| 10% (cautious: only 1 year in 10 freezes later) | Jun 3 |
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 6 |
| 50% (the "average" first frost) | Sep 20 |
| 90% (late: most years have frozen by now) | Sep 30 |
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 21 | Sep 20 |
| 28°F (hard freeze) | May 10 | Sep 27 |
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 59218
Dates count from your average last spring frost (May 21) and first fall frost (Sep 20). 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 26–Apr 9 | May 28–Jun 11 (transplant) | – |
| Pepper (sweet and hot) | Mar 12–26 | Jun 4–18 (transplant) | – |
| Eggplant | Mar 12–26 | Jun 4–18 (transplant) | – |
| Tomatillo | Mar 26–Apr 9 | May 28–Jun 11 (transplant) | – |
| Lettuce | Mar 26–Apr 9 | Apr 30–May 21 (transplant) Apr 23–Jun 4 (sow outdoors) | Jul 26–Aug 16 (transplant) Jul 12–Aug 9 (sowing) |
| Spinach | – | Apr 9–30 (sow outdoors) | Jul 26–Aug 16 (sowing) |
| Kale | Mar 26–Apr 9 | Apr 23–May 7 (transplant) Apr 23–May 7 (sow outdoors) | Jun 28–Jul 26 (transplant) Jun 14–Jul 12 (sowing) |
| Collards | Mar 26–Apr 9 | Apr 23–May 21 (transplant) Apr 23–May 21 (sow outdoors) | Jun 28–Jul 26 (transplant) Jun 14–Jul 12 (sowing) |
| Broccoli | Mar 12–26 | Apr 23–May 7 (transplant) | Jun 14–Jul 12 (transplant) |
| Cabbage | Mar 12–26 | Apr 23–May 7 (transplant) | Jun 14–Jul 12 (transplant) |
| Cauliflower | Mar 12–26 | May 7–21 (transplant) | Jun 14–Jul 12 (transplant) |
| Brussels sprouts | Feb 26–Mar 12 | Apr 23–May 7 (transplant) | May 31–Jun 21 (transplant) |
| Kohlrabi | Mar 26–Apr 9 | Apr 23–May 7 (transplant) Apr 23–May 7 (sow outdoors) | Jul 12–26 (sowing) |
| Bok choy / Asian greens | – | Apr 23–May 7 (sow outdoors) | Jul 26–Aug 9 (sowing) |
| Arugula | – | Apr 23–May 21 (sow outdoors) | Jul 26–Aug 23 (sowing) |
| Mustard greens | – | Apr 23–May 14 (sow outdoors) | Jul 26–Aug 9 (sowing) |
| Swiss chard | Apr 9–23 | May 7–28 (transplant) May 7–Jun 4 (sow outdoors) | Jul 12–26 (sowing) |
| Beet | – | Apr 23–May 21 (sow outdoors) | Jul 12–26 (sowing) |
| Carrot | – | Apr 30–May 28 (sow outdoors) | Jun 28–Jul 12 (sowing) |
| Radish | – | Apr 16–May 28 (sow outdoors) | Aug 9–23 (sowing) |
| Turnip | – | Apr 23–May 14 (sow outdoors) | Jul 12–26 (sowing) |
| Parsnip | – | Apr 30–May 21 (sow outdoors) | – |
| Pea (garden, snap, snow) | – | Mar 26–Apr 23 (sow outdoors) | Jun 28–Jul 12 (sowing) |
| Onion (bulbing) | Feb 26–Mar 12 | Apr 9–23 (transplant) | – |
| Green onion / scallion | – | Apr 9–May 7 (sow outdoors) | Jul 12–26 (sowing) |
| Leek | Feb 26–Mar 12 | Apr 23–May 7 (transplant) | – |
| Garlic | – | – | Aug 9–Sep 6 (sowing) |
| Shallot | – | Apr 9–23 (transplant) | Aug 9–Sep 6 (sowing) |
| Potato | – | Apr 23–May 7 (transplant) | May 31–Jun 14 (transplant) |
| Sweet potato | – | Jun 11–25 (transplant) | – |
| Sweet corn | – | May 28–Jun 11 (sow outdoors) | – |
| Bean, bush (snap) | – | May 28–Jun 11 (sow outdoors) | – |
| Bean, pole | – | May 28–Jun 11 (sow outdoors) | – |
| Lima bean | – | Jun 4–18 (sow outdoors) | – |
| Southern pea (cowpea, black-eyed pea) | – | Jun 11–Jul 2 (sow outdoors) | – |
| Cucumber | Apr 23–30 | May 28–Jun 11 (transplant) May 28–Jun 11 (sow outdoors) | – |
| Summer squash / zucchini | Apr 23–30 | May 28–Jun 11 (transplant) May 28–Jun 11 (sow outdoors) | – |
| Winter squash | Apr 23–30 | May 28–Jun 11 (transplant) May 28–Jun 11 (sow outdoors) | – |
| Pumpkin | – | May 28–Jun 11 (sow outdoors) | – |
| Watermelon | Apr 23–30 | Jun 4–18 (transplant) Jun 4–18 (sow outdoors) | – |
| Cantaloupe / muskmelon | Apr 23–30 | Jun 4–18 (transplant) Jun 4–18 (sow outdoors) | – |
| Okra | Apr 9–23 | Jun 4–18 (transplant) Jun 4–18 (sow outdoors) | – |
| Celery | Feb 26–Mar 12 | May 28–Jun 4 (transplant) | – |
| Basil | Apr 9–23 | May 28–Jun 11 (transplant) May 28–Jun 11 (sow outdoors) | – |
| Cilantro | – | May 7–Jun 4 (sow outdoors) | Jul 26–Aug 9 (sowing) |
| Parsley | Mar 12–26 | May 7–21 (transplant) Apr 30–May 21 (sow outdoors) | – |
| Dill | – | May 21–Jun 4 (sow outdoors) | Jul 26–Aug 9 (sowing) |
| Sunflower | – | May 21–Jun 4 (sow outdoors) | – |
| Asparagus (crowns) | – | Apr 23–May 7 (transplant) | – |
| Rhubarb (crowns) | – | Apr 23–May 7 (transplant) | – |
| Strawberry (plants) | – | Apr 23–May 7 (transplant) | Jul 12–Aug 9 (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: Culbertson, MT (NOAA GHCN-Daily ID USC00242122), elevation 1,940 ft, 5.2 miles from the ZIP's center point. NOAA completeness flag: S (standard, 24+ years).
Nearby stations
| Station | Distance | Last frost (50%) | First frost (50%) |
|---|---|---|---|
| Medicine Lake 3 SE, MT | 28 mi | May 16 | Sep 18 |
| Sidney, MT | 29 mi | May 11 | Sep 27 |
| Wolf Point 29 ENE, MT | 32 mi | May 24 | Sep 14 |
The average last-frost dates of these stations span 13 days, a rough guide to local variation. See data sources & methods.
Frost questions for 59218
When is the last frost in 59218?
The average (50% chance) last spring freeze of 32°F for ZIP 59218 is May 21. For a more cautious planting date, use June 3, when only 1 year in 10 still sees a later freeze.
When is the first frost in 59218?
The average first fall freeze is September 20. In 1 year in 10 it comes by September 6.
What hardiness zone is 59218?
ZIP 59218 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 59218 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
59226 Froid 59212 Bainville 59221 Fairview 59213 Brockton 59242 Homestead 59243 Fox Lake 59247 Medicine Lake 59255 Poplar
Other ZIP codes in Roosevelt County
59201 59212 59213 59226 59255 All Roosevelt County frost dates · Montana 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.