Fall in zone 5aPhoto: Dietmar Rabich, CC BY-SA 4.0, via Wikimedia Commons
Frost dates for ZIP 59720 (Madison 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, Hebgen Dam, MT (13 miles away).
- Average last spring frostJun 1550% 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)87 daysmedian, 32°F threshold
- USDA hardiness zone5a-20 to -15°F avg. coldest night
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Frost and freeze alerts from the NWS forecast for 59720, 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
44°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 Table Mountain (60 mi).
4-inch depth
43°F Below 50°F
24-hour average · latest 46°F, as of Oct 18, 2:00 AM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Table Mountain (60 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 59720 load here. You can also open the NWS forecast for this ZIP.
Pre-emergent
Soil is 43°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 29 |
| 50% (the "average" last frost) | Jun 15 |
| 10% (cautious: only 1 year in 10 freezes later) | Jul 7 |
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 27 |
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 15 | Sep 10 |
| 28°F (hard freeze) | May 24 | Sep 26 |
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 59720
Dates count from your average last spring frost (Jun 15) 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 20–May 4 | Jun 22–Jul 6 (transplant) | – |
| Pepper (sweet and hot) | Apr 6–20 | Jun 29–Jul 13 (transplant) | – |
| Eggplant | Apr 6–20 | Jun 29–Jul 13 (transplant) | – |
| Tomatillo | Apr 20–May 4 | Jun 22–Jul 6 (transplant) | – |
| Lettuce | Apr 20–May 4 | May 25–Jun 15 (transplant) May 18–Jun 29 (sow outdoors) | Jul 16–Aug 6 (transplant) Jul 2–30 (sowing) |
| Spinach | – | May 4–25 (sow outdoors) | Jul 16–Aug 6 (sowing) |
| Kale | Apr 20–May 4 | May 18–Jun 1 (transplant) May 18–Jun 1 (sow outdoors) | Jun 18–Jul 16 (transplant) Jun 4–Jul 2 (sowing) |
| Collards | Apr 20–May 4 | May 18–Jun 15 (transplant) May 18–Jun 15 (sow outdoors) | Jun 18–Jul 16 (transplant) |
| Broccoli | Apr 6–20 | May 18–Jun 1 (transplant) | Jun 4–Jul 2 (transplant) |
| Cabbage | Apr 6–20 | May 18–Jun 1 (transplant) | Jun 4–Jul 2 (transplant) |
| Cauliflower | Apr 6–20 | Jun 1–15 (transplant) | – |
| Brussels sprouts | Mar 23–Apr 6 | May 18–Jun 1 (transplant) | – |
| Kohlrabi | Apr 20–May 4 | May 18–Jun 1 (transplant) May 18–Jun 1 (sow outdoors) | Jul 2–16 (sowing) |
| Bok choy / Asian greens | – | May 18–Jun 1 (sow outdoors) | Jul 16–30 (sowing) |
| Arugula | – | May 18–Jun 15 (sow outdoors) | Jul 16–Aug 13 (sowing) |
| Mustard greens | – | May 18–Jun 8 (sow outdoors) | Jul 16–30 (sowing) |
| Swiss chard | May 4–18 | Jun 1–22 (transplant) Jun 1–29 (sow outdoors) | Jul 2–16 (sowing) |
| Beet | – | May 18–Jun 15 (sow outdoors) | Jul 2–16 (sowing) |
| Carrot | – | May 25–Jun 22 (sow outdoors) | – |
| Radish | – | May 11–Jun 22 (sow outdoors) | Jul 30–Aug 13 (sowing) |
| Turnip | – | May 18–Jun 8 (sow outdoors) | Jul 2–16 (sowing) |
| Parsnip | – | May 25–Jun 15 (sow outdoors) | – |
| Pea (garden, snap, snow) | – | Apr 20–May 18 (sow outdoors) | Jun 18–Jul 2 (sowing) |
| Onion (bulbing) | Mar 23–Apr 6 | May 4–18 (transplant) | – |
| Green onion / scallion | – | May 4–Jun 1 (sow outdoors) | Jul 2–16 (sowing) |
| Leek | Mar 23–Apr 6 | May 18–Jun 1 (transplant) | – |
| Garlic | – | – | Jul 30–Aug 27 (sowing) |
| Shallot | – | May 4–18 (transplant) | Jul 30–Aug 27 (sowing) |
| Potato | – | May 18–Jun 1 (transplant) | – |
| Sweet potato | – | Jul 6–20 (transplant) | – |
| Sweet corn | – | Jun 22–Jul 6 (sow outdoors) | – |
| Bean, bush (snap) | – | Jun 22–Jul 6 (sow outdoors) | – |
| Bean, pole | – | Jun 22–Jul 6 (sow outdoors) | – |
| Lima bean | – | Jun 29–Jul 13 (sow outdoors) | – |
| Southern pea (cowpea, black-eyed pea) | – | Jul 6–27 (sow outdoors) | – |
| Cucumber | May 18–25 | Jun 22–Jul 6 (transplant) Jun 22–Jul 6 (sow outdoors) | – |
| Summer squash / zucchini | May 18–25 | Jun 22–Jul 6 (transplant) Jun 22–Jul 6 (sow outdoors) | – |
| Winter squash | May 18–25 | Jun 22–Jul 6 (transplant) Jun 22–Jul 6 (sow outdoors) | – |
| Pumpkin | – | Jun 22–Jul 6 (sow outdoors) | – |
| Watermelon | May 18–25 | Jun 29–Jul 13 (transplant) Jun 29–Jul 13 (sow outdoors) | – |
| Cantaloupe / muskmelon | May 18–25 | Jun 29–Jul 13 (transplant) Jun 29–Jul 13 (sow outdoors) | – |
| Okra | May 4–18 | Jun 29–Jul 13 (transplant) Jun 29–Jul 13 (sow outdoors) | – |
| Celery | Mar 23–Apr 6 | Jun 22–29 (transplant) | – |
| Basil | May 4–18 | Jun 22–Jul 6 (transplant) Jun 22–Jul 6 (sow outdoors) | – |
| Cilantro | – | Jun 1–29 (sow outdoors) | Jul 16–30 (sowing) |
| Parsley | Apr 6–20 | Jun 1–15 (transplant) May 25–Jun 15 (sow outdoors) | – |
| Dill | – | Jun 15–29 (sow outdoors) | Jul 16–30 (sowing) |
| Sunflower | – | Jun 15–29 (sow outdoors) | – |
| Asparagus (crowns) | – | May 18–Jun 1 (transplant) | – |
| Rhubarb (crowns) | – | May 18–Jun 1 (transplant) | – |
| Strawberry (plants) | – | May 18–Jun 1 (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: Hebgen Dam, MT (NOAA GHCN-Daily ID USC00244038), elevation 6,489 ft, 13.2 miles from the ZIP's center point. NOAA completeness flag: R (representative, 10+ years).
Nearby stations
| Station | Distance | Last frost (50%) | First frost (50%) |
|---|---|---|---|
| Alder 17 S, MT | 25 mi | Jun 6 | Sep 14 |
| Ennis, MT | 28 mi | Jun 16 | Sep 4 |
| Virginia City, MT | 30 mi | Jun 4 | Sep 18 |
The average last-frost dates of these stations span 12 days, a rough guide to local variation. See data sources & methods.
Frost questions for 59720
When is the last frost in 59720?
The average (50% chance) last spring freeze of 32°F for ZIP 59720 is June 15. For a more cautious planting date, use July 7, when only 1 year in 10 still sees a later freeze.
When is the first frost in 59720?
The average first fall freeze is September 10. In 1 year in 10 it comes by August 25.
What hardiness zone is 59720?
ZIP 59720 is in USDA zone 5a (-20 to -15°F average coldest winter night), per the 2023 USDA Plant Hardiness Zone Map ZIP listing.
What is the soil temperature in 59720 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
59758 West Yellowstone 59710 Alder 59716 Big Sky 59729 Ennis 59755 Virginia City 59730 Big Sky 83429 Island Park 83433 Island Park
Other ZIP codes in Madison County
59710 59716 59729 59735 59740 59745 59747 59749 59751 59754 59755 All Madison 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.