Fall in zone 4aPhoto: Dietmar Rabich, CC BY-SA 4.0, via Wikimedia Commons
Frost dates for ZIP 59483 (Sun River, 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, Sun Rvr 4 S, MT (1 miles away).
- Average last spring frostJun 250% chance of a 32°F freeze after this date
- Average first fall frostSep 1050% chance of a 32°F freeze by this date
- Growing season (frost-free)96 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
46°F Below 50°F
24-hour average · latest 45°F, as of Oct 18, 2:00 AM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Conrad Ag Rc (59 mi).
4-inch depth
46°F Below 50°F
24-hour average · latest 47°F, as of Oct 18, 2:00 AM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Conrad Ag Rc (59 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 59483 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 18 |
| 50% (the "average" last frost) | Jun 2 |
| 10% (cautious: only 1 year in 10 freezes later) | Jun 21 |
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 25 |
| 50% (the "average" first frost) | Sep 10 |
| 90% (late: most years have frozen by now) | Sep 25 |
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 2 | Sep 10 |
| 28°F (hard freeze) | May 18 | 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 59483
Dates count from your average last spring frost (Jun 2) and first fall frost (Sep 10). 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 7–21 | Jun 9–23 (transplant) | – |
| Pepper (sweet and hot) | Mar 24–Apr 7 | Jun 16–30 (transplant) | – |
| Eggplant | Mar 24–Apr 7 | Jun 16–30 (transplant) | – |
| Tomatillo | Apr 7–21 | Jun 9–23 (transplant) | – |
| Lettuce | Apr 7–21 | May 12–Jun 2 (transplant) May 5–Jun 16 (sow outdoors) | Jul 16–Aug 6 (transplant) Jul 2–30 (sowing) |
| Spinach | – | Apr 21–May 12 (sow outdoors) | Jul 16–Aug 6 (sowing) |
| Kale | Apr 7–21 | May 5–19 (transplant) May 5–19 (sow outdoors) | Jun 18–Jul 16 (transplant) Jun 4–Jul 2 (sowing) |
| Collards | Apr 7–21 | May 5–Jun 2 (transplant) May 5–Jun 2 (sow outdoors) | Jun 18–Jul 16 (transplant) Jun 4–Jul 2 (sowing) |
| Broccoli | Mar 24–Apr 7 | May 5–19 (transplant) | Jun 4–Jul 2 (transplant) |
| Cabbage | Mar 24–Apr 7 | May 5–19 (transplant) | Jun 4–Jul 2 (transplant) |
| Cauliflower | Mar 24–Apr 7 | May 19–Jun 2 (transplant) | Jun 4–Jul 2 (transplant) |
| Brussels sprouts | Mar 10–24 | May 5–19 (transplant) | May 21–Jun 11 (transplant) |
| Kohlrabi | Apr 7–21 | May 5–19 (transplant) May 5–19 (sow outdoors) | Jul 2–16 (sowing) |
| Bok choy / Asian greens | – | May 5–19 (sow outdoors) | Jul 16–30 (sowing) |
| Arugula | – | May 5–Jun 2 (sow outdoors) | Jul 16–Aug 13 (sowing) |
| Mustard greens | – | May 5–26 (sow outdoors) | Jul 16–30 (sowing) |
| Swiss chard | Apr 21–May 5 | May 19–Jun 9 (transplant) May 19–Jun 16 (sow outdoors) | Jul 2–16 (sowing) |
| Beet | – | May 5–Jun 2 (sow outdoors) | Jul 2–16 (sowing) |
| Carrot | – | May 12–Jun 9 (sow outdoors) | Jun 18–Jul 2 (sowing) |
| Radish | – | Apr 28–Jun 9 (sow outdoors) | Jul 30–Aug 13 (sowing) |
| Turnip | – | May 5–26 (sow outdoors) | Jul 2–16 (sowing) |
| Parsnip | – | May 12–Jun 2 (sow outdoors) | – |
| Pea (garden, snap, snow) | – | Apr 7–May 5 (sow outdoors) | Jun 18–Jul 2 (sowing) |
| Onion (bulbing) | Mar 10–24 | Apr 21–May 5 (transplant) | – |
| Green onion / scallion | – | Apr 21–May 19 (sow outdoors) | Jul 2–16 (sowing) |
| Leek | Mar 10–24 | May 5–19 (transplant) | – |
| Garlic | – | – | Jul 30–Aug 27 (sowing) |
| Shallot | – | Apr 21–May 5 (transplant) | Jul 30–Aug 27 (sowing) |
| Potato | – | May 5–19 (transplant) | May 21–Jun 4 (transplant) |
| Sweet potato | – | Jun 23–Jul 7 (transplant) | – |
| Sweet corn | – | Jun 9–23 (sow outdoors) | – |
| Bean, bush (snap) | – | Jun 9–23 (sow outdoors) | – |
| Bean, pole | – | Jun 9–23 (sow outdoors) | – |
| Lima bean | – | Jun 16–30 (sow outdoors) | – |
| Southern pea (cowpea, black-eyed pea) | – | Jun 23–Jul 14 (sow outdoors) | – |
| Cucumber | May 5–12 | Jun 9–23 (transplant) Jun 9–23 (sow outdoors) | – |
| Summer squash / zucchini | May 5–12 | Jun 9–23 (transplant) Jun 9–23 (sow outdoors) | – |
| Winter squash | May 5–12 | Jun 9–23 (transplant) Jun 9–23 (sow outdoors) | – |
| Pumpkin | – | Jun 9–23 (sow outdoors) | – |
| Watermelon | May 5–12 | Jun 16–30 (transplant) Jun 16–30 (sow outdoors) | – |
| Cantaloupe / muskmelon | May 5–12 | Jun 16–30 (transplant) Jun 16–30 (sow outdoors) | – |
| Okra | Apr 21–May 5 | Jun 16–30 (transplant) Jun 16–30 (sow outdoors) | – |
| Celery | Mar 10–24 | Jun 9–16 (transplant) | – |
| Basil | Apr 21–May 5 | Jun 9–23 (transplant) Jun 9–23 (sow outdoors) | – |
| Cilantro | – | May 19–Jun 16 (sow outdoors) | Jul 16–30 (sowing) |
| Parsley | Mar 24–Apr 7 | May 19–Jun 2 (transplant) May 12–Jun 2 (sow outdoors) | – |
| Dill | – | Jun 2–16 (sow outdoors) | Jul 16–30 (sowing) |
| Sunflower | – | Jun 2–16 (sow outdoors) | – |
| Asparagus (crowns) | – | May 5–19 (transplant) | – |
| Rhubarb (crowns) | – | May 5–19 (transplant) | – |
| Strawberry (plants) | – | May 5–19 (transplant) | Jul 2–30 (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: Sun Rvr 4 S, MT (NOAA GHCN-Daily ID USC00248021), elevation 3,600 ft, 0.9 miles from the ZIP's center point. NOAA completeness flag: S (standard, 24+ years).
Nearby stations
| Station | Distance | Last frost (50%) | First frost (50%) |
|---|---|---|---|
| Fairfield, MT | 16 mi | May 13 | Sep 27 |
| Great Falls WFO, MT | 16 mi | May 12 | Sep 28 |
| Great Falls Intl AP, MT | 16 mi | May 19 | Sep 24 |
The average last-frost dates of these stations span 21 days, a rough guide to local variation. See data sources & methods.
Frost questions for 59483
When is the last frost in 59483?
The average (50% chance) last spring freeze of 32°F for ZIP 59483 is June 2. For a more cautious planting date, use June 21, when only 1 year in 10 still sees a later freeze.
When is the first frost in 59483?
The average first fall freeze is September 10. In 1 year in 10 it comes by August 25.
What hardiness zone is 59483?
ZIP 59483 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 59483 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
59485 Ulm 59443 Fort Shaw 59487 Vaughn 59477 Simms 59468 Power 59436 Fairfield 59401 Great Falls 59404 Sun Prairie
Other ZIP codes in Cascade County
59401 59404 59405 59412 59414 59421 59443 59463 59465 59472 59477 59480 59485 59487 All Cascade County frost dates · Montana frost dates
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Weekly yard timing, plus frost and soil-temperature alerts for your ZIP code.
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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.