Frost dates for ZIP 59055 (Sweet Grass County, 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, Melville 4 W, MT (11 miles away).
- Average last spring frostJun 950% chance of a 32°F freeze after this date
- Average first fall frostSep 750% chance of a 32°F freeze by this date
- Growing season (frost-free)88 daysmedian, 32°F threshold
- USDA hardiness zone4b-25 to -20°F avg. coldest night
This week in your yard
As of Oct 18, 2026, from your frost dates, zone and soil temperature. Lawn timing · Vegetables · Pruning · Plants
Fall in zone 4b
Soil temperature now
2-inch depth
41°F Below 50°F
24-hour average · latest 38°F, as of Oct 18, 8:00 AM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Lewistown 42 WSW (58 mi).
4-inch depth
42°F Below 50°F
24-hour average · latest 41°F, as of Oct 18, 8:00 AM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Lewistown 42 WSW (58 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 59055 load here. You can also open the NWS forecast for this ZIP.
Pre-emergent
Soil is 42°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 26 |
| 50% (the "average" last frost) | Jun 9 |
| 10% (cautious: only 1 year in 10 freezes later) | Jun 27 |
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) | Aug 21 |
| 50% (the "average" first frost) | Sep 7 |
| 90% (late: most years have frozen by now) | Sep 23 |
Light frost, freeze and hard freeze
| Threshold | Last spring (50%) | First fall (50%) |
|---|---|---|
| 36°F (light frost possible on clear, calm nights) | n/a | n/a |
| 32°F (freeze) | Jun 9 | Sep 7 |
| 28°F (hard freeze) | May 24 | Sep 22 |
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 59055
Dates count from your average last spring frost (Jun 9) and first fall frost (Sep 7). 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 | Apr 14–28 | Jun 16–30 (transplant) | – |
| Pepper (sweet and hot) | Mar 31–Apr 14 | Jun 23–Jul 7 (transplant) | – |
| Eggplant | Mar 31–Apr 14 | Jun 23–Jul 7 (transplant) | – |
| Tomatillo | Apr 14–28 | Jun 16–30 (transplant) | – |
| Lettuce | Apr 14–28 | May 19–Jun 9 (transplant) May 12–Jun 23 (sow outdoors) | Jul 13–Aug 3 (transplant) Jun 29–Jul 27 (sowing) |
| Spinach | – | Apr 28–May 19 (sow outdoors) | Jul 13–Aug 3 (sowing) |
| Kale | Apr 14–28 | May 12–26 (transplant) May 12–26 (sow outdoors) | Jun 15–Jul 13 (transplant) Jun 1–29 (sowing) |
| Collards | Apr 14–28 | May 12–Jun 9 (transplant) May 12–Jun 9 (sow outdoors) | Jun 15–Jul 13 (transplant) |
| Broccoli | Mar 31–Apr 14 | May 12–26 (transplant) | Jun 1–29 (transplant) |
| Cabbage | Mar 31–Apr 14 | May 12–26 (transplant) | Jun 1–29 (transplant) |
| Cauliflower | Mar 31–Apr 14 | May 26–Jun 9 (transplant) | – |
| Brussels sprouts | Mar 17–31 | May 12–26 (transplant) | – |
| Kohlrabi | Apr 14–28 | May 12–26 (transplant) May 12–26 (sow outdoors) | Jun 29–Jul 13 (sowing) |
| Bok choy / Asian greens | – | May 12–26 (sow outdoors) | Jul 13–27 (sowing) |
| Arugula | – | May 12–Jun 9 (sow outdoors) | Jul 13–Aug 10 (sowing) |
| Mustard greens | – | May 12–Jun 2 (sow outdoors) | Jul 13–27 (sowing) |
| Swiss chard | Apr 28–May 12 | May 26–Jun 16 (transplant) May 26–Jun 23 (sow outdoors) | Jun 29–Jul 13 (sowing) |
| Beet | – | May 12–Jun 9 (sow outdoors) | Jun 29–Jul 13 (sowing) |
| Carrot | – | May 19–Jun 16 (sow outdoors) | – |
| Radish | – | May 5–Jun 16 (sow outdoors) | Jul 27–Aug 10 (sowing) |
| Turnip | – | May 12–Jun 2 (sow outdoors) | Jun 29–Jul 13 (sowing) |
| Parsnip | – | May 19–Jun 9 (sow outdoors) | – |
| Pea (garden, snap, snow) | – | Apr 14–May 12 (sow outdoors) | Jun 15–29 (sowing) |
| Onion (bulbing) | Mar 17–31 | Apr 28–May 12 (transplant) | – |
| Green onion / scallion | – | Apr 28–May 26 (sow outdoors) | Jun 29–Jul 13 (sowing) |
| Leek | Mar 17–31 | May 12–26 (transplant) | – |
| Garlic | – | – | Jul 27–Aug 24 (sowing) |
| Shallot | – | Apr 28–May 12 (transplant) | Jul 27–Aug 24 (sowing) |
| Potato | – | May 12–26 (transplant) | – |
| Sweet potato | – | Jun 30–Jul 14 (transplant) | – |
| Sweet corn | – | Jun 16–30 (sow outdoors) | – |
| Bean, bush (snap) | – | Jun 16–30 (sow outdoors) | – |
| Bean, pole | – | Jun 16–30 (sow outdoors) | – |
| Lima bean | – | Jun 23–Jul 7 (sow outdoors) | – |
| Southern pea (cowpea, black-eyed pea) | – | Jun 30–Jul 21 (sow outdoors) | – |
| Cucumber | May 12–19 | Jun 16–30 (transplant) Jun 16–30 (sow outdoors) | – |
| Summer squash / zucchini | May 12–19 | Jun 16–30 (transplant) Jun 16–30 (sow outdoors) | – |
| Winter squash | May 12–19 | Jun 16–30 (transplant) Jun 16–30 (sow outdoors) | – |
| Pumpkin | – | Jun 16–30 (sow outdoors) | – |
| Watermelon | May 12–19 | Jun 23–Jul 7 (transplant) Jun 23–Jul 7 (sow outdoors) | – |
| Cantaloupe / muskmelon | May 12–19 | Jun 23–Jul 7 (transplant) Jun 23–Jul 7 (sow outdoors) | – |
| Okra | Apr 28–May 12 | Jun 23–Jul 7 (transplant) Jun 23–Jul 7 (sow outdoors) | – |
| Celery | Mar 17–31 | Jun 16–23 (transplant) | – |
| Basil | Apr 28–May 12 | Jun 16–30 (transplant) Jun 16–30 (sow outdoors) | – |
| Cilantro | – | May 26–Jun 23 (sow outdoors) | Jul 13–27 (sowing) |
| Parsley | Mar 31–Apr 14 | May 26–Jun 9 (transplant) May 19–Jun 9 (sow outdoors) | – |
| Dill | – | Jun 9–23 (sow outdoors) | Jul 13–27 (sowing) |
| Sunflower | – | Jun 9–23 (sow outdoors) | – |
| Asparagus (crowns) | – | May 12–26 (transplant) | – |
| Rhubarb (crowns) | – | May 12–26 (transplant) | – |
| Strawberry (plants) | – | May 12–26 (transplant) | Jun 29–Jul 27 (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: Melville 4 W, MT (NOAA GHCN-Daily ID USC00245603), elevation 5,365 ft, 11.5 miles from the ZIP's center point. NOAA completeness flag: S (standard, 24+ years).
Nearby stations
| Station | Distance | Last frost (50%) | First frost (50%) |
|---|---|---|---|
| Gibson 2 NE, MT | 16 mi | May 27 | Sep 18 |
| Big Timber, MT | 20 mi | May 14 | Sep 26 |
| Harlowton, MT | 23 mi | May 23 | Sep 16 |
The average last-frost dates of these stations span 26 days, a rough guide to local variation. See data sources & methods.
Frost questions for 59055
When is the last frost in 59055?
The average (50% chance) last spring freeze of 32°F for ZIP 59055 is June 9. For a more cautious planting date, use June 27, when only 1 year in 10 still sees a later freeze.
When is the first frost in 59055?
The average first fall freeze is September 7. In 1 year in 10 it comes by August 21.
What hardiness zone is 59055?
ZIP 59055 is in USDA zone 4b (-25 to -20°F average coldest winter night), per the 2023 USDA Plant Hardiness Zone Map ZIP listing.
What is the soil temperature in 59055 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
59011 Big Timber 59085 Twodot 59036 Harlowton 59078 Shawmut 59033 Greycliff 59069 Reed Point 59082 Springdale 59067 Rapelje
Other ZIP codes in Sweet Grass County
59011 59033 59052 All Sweet Grass County frost dates · Montana frost dates
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