Fall in zone 5bPhoto: Dietmar Rabich, CC BY-SA 4.0, via Wikimedia Commons
Frost dates for ZIP 59820 (Cyr, 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, Alberton, MT (10 miles away).
- Average last spring frostMay 1850% chance of a 32°F freeze after this date
- Average first fall frostSep 2550% chance of a 32°F freeze by this date
- Growing season (frost-free)126 daysmedian, 32°F threshold
- USDA hardiness zone5b-15 to -10°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
No soil station with a fresh reading within 62 miles.
4-inch depth
No soil station with a fresh reading within 62 miles.
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 59820 load here. You can also open the NWS forecast for this ZIP.
Pre-emergent
No soil reading near this ZIP. Typical extension timing for your region: spring 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 5 |
| 50% (the "average" last frost) | May 18 |
| 10% (cautious: only 1 year in 10 freezes later) | Jun 6 |
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 25 |
| 90% (late: most years have frozen by now) | Oct 6 |
Light frost, freeze and hard freeze
| Threshold | Last spring (50%) | First fall (50%) |
|---|---|---|
| 36°F (light frost possible on clear, calm nights) | Jun 11 | Sep 9 |
| 32°F (freeze) | May 18 | Sep 25 |
| 28°F (hard freeze) | May 3 | Oct 5 |
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 59820
Dates count from your average last spring frost (May 18) and first fall frost (Sep 25). 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 23–Apr 6 | May 25–Jun 8 (transplant) | – |
| Pepper (sweet and hot) | Mar 9–23 | Jun 1–15 (transplant) | – |
| Eggplant | Mar 9–23 | Jun 1–15 (transplant) | – |
| Tomatillo | Mar 23–Apr 6 | May 25–Jun 8 (transplant) | – |
| Lettuce | Mar 23–Apr 6 | Apr 27–May 18 (transplant) Apr 20–Jun 1 (sow outdoors) | Jul 31–Aug 21 (transplant) Jul 17–Aug 14 (sowing) |
| Spinach | – | Apr 6–27 (sow outdoors) | Jul 31–Aug 21 (sowing) |
| Kale | Mar 23–Apr 6 | Apr 20–May 4 (transplant) Apr 20–May 4 (sow outdoors) | Jul 3–31 (transplant) Jun 19–Jul 17 (sowing) |
| Collards | Mar 23–Apr 6 | Apr 20–May 18 (transplant) Apr 20–May 18 (sow outdoors) | Jul 3–31 (transplant) Jun 19–Jul 17 (sowing) |
| Broccoli | Mar 9–23 | Apr 20–May 4 (transplant) | Jun 19–Jul 17 (transplant) |
| Cabbage | Mar 9–23 | Apr 20–May 4 (transplant) | Jun 19–Jul 17 (transplant) |
| Cauliflower | Mar 9–23 | May 4–18 (transplant) | Jun 19–Jul 17 (transplant) |
| Brussels sprouts | Feb 23–Mar 9 | Apr 20–May 4 (transplant) | Jun 5–26 (transplant) |
| Kohlrabi | Mar 23–Apr 6 | Apr 20–May 4 (transplant) Apr 20–May 4 (sow outdoors) | Jul 17–31 (sowing) |
| Bok choy / Asian greens | – | Apr 20–May 4 (sow outdoors) | Jul 31–Aug 14 (sowing) |
| Arugula | – | Apr 20–May 18 (sow outdoors) | Jul 31–Aug 28 (sowing) |
| Mustard greens | – | Apr 20–May 11 (sow outdoors) | Jul 31–Aug 14 (sowing) |
| Swiss chard | Apr 6–20 | May 4–25 (transplant) May 4–Jun 1 (sow outdoors) | Jul 17–31 (sowing) |
| Beet | – | Apr 20–May 18 (sow outdoors) | Jul 17–31 (sowing) |
| Carrot | – | Apr 27–May 25 (sow outdoors) | Jul 3–17 (sowing) |
| Radish | – | Apr 13–May 25 (sow outdoors) | Aug 14–28 (sowing) |
| Turnip | – | Apr 20–May 11 (sow outdoors) | Jul 17–31 (sowing) |
| Parsnip | – | Apr 27–May 18 (sow outdoors) | – |
| Pea (garden, snap, snow) | – | Mar 23–Apr 20 (sow outdoors) | Jul 3–17 (sowing) |
| Onion (bulbing) | Feb 23–Mar 9 | Apr 6–20 (transplant) | – |
| Green onion / scallion | – | Apr 6–May 4 (sow outdoors) | Jul 17–31 (sowing) |
| Leek | Feb 23–Mar 9 | Apr 20–May 4 (transplant) | – |
| Garlic | – | – | Aug 14–Sep 11 (sowing) |
| Shallot | – | Apr 6–20 (transplant) | Aug 14–Sep 11 (sowing) |
| Potato | – | Apr 20–May 4 (transplant) | Jun 5–19 (transplant) |
| Sweet potato | – | Jun 8–22 (transplant) | – |
| Sweet corn | – | May 25–Jun 8 (sow outdoors) | – |
| Bean, bush (snap) | – | May 25–Jun 8 (sow outdoors) | – |
| Bean, pole | – | May 25–Jun 8 (sow outdoors) | – |
| Lima bean | – | Jun 1–15 (sow outdoors) | – |
| Southern pea (cowpea, black-eyed pea) | – | Jun 8–29 (sow outdoors) | – |
| Cucumber | Apr 20–27 | May 25–Jun 8 (transplant) May 25–Jun 8 (sow outdoors) | – |
| Summer squash / zucchini | Apr 20–27 | May 25–Jun 8 (transplant) May 25–Jun 8 (sow outdoors) | – |
| Winter squash | Apr 20–27 | May 25–Jun 8 (transplant) May 25–Jun 8 (sow outdoors) | – |
| Pumpkin | – | May 25–Jun 8 (sow outdoors) | – |
| Watermelon | Apr 20–27 | Jun 1–15 (transplant) Jun 1–15 (sow outdoors) | – |
| Cantaloupe / muskmelon | Apr 20–27 | Jun 1–15 (transplant) Jun 1–15 (sow outdoors) | – |
| Okra | Apr 6–20 | Jun 1–15 (transplant) Jun 1–15 (sow outdoors) | – |
| Celery | Feb 23–Mar 9 | May 25–Jun 1 (transplant) | – |
| Basil | Apr 6–20 | May 25–Jun 8 (transplant) May 25–Jun 8 (sow outdoors) | – |
| Cilantro | – | May 4–Jun 1 (sow outdoors) | Jul 31–Aug 14 (sowing) |
| Parsley | Mar 9–23 | May 4–18 (transplant) Apr 27–May 18 (sow outdoors) | – |
| Dill | – | May 18–Jun 1 (sow outdoors) | Jul 31–Aug 14 (sowing) |
| Sunflower | – | May 18–Jun 1 (sow outdoors) | – |
| Asparagus (crowns) | – | Apr 20–May 4 (transplant) | – |
| Rhubarb (crowns) | – | Apr 20–May 4 (transplant) | – |
| Strawberry (plants) | – | Apr 20–May 4 (transplant) | Jul 17–Aug 14 (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: Alberton, MT (NOAA GHCN-Daily ID USC00240075), elevation 3,060 ft, 9.6 miles from the ZIP's center point. NOAA completeness flag: R (representative, 10+ years).
Nearby stations
| Station | Distance | Last frost (50%) | First frost (50%) |
|---|---|---|---|
| Superior, MT | 24 mi | May 17 | Sep 23 |
| Missoula Intl AP, MT | 24 mi | May 16 | Sep 26 |
| Missoula 6 NW WFO, MT | 25 mi | May 6 | Oct 4 |
The average last-frost dates of these stations span 12 days, a rough guide to local variation. See data sources & methods.
Frost questions for 59820
When is the last frost in 59820?
The average (50% chance) last spring freeze of 32°F for ZIP 59820 is May 18. For a more cautious planting date, use June 6, when only 1 year in 10 still sees a later freeze.
When is the first frost in 59820?
The average first fall freeze is September 25. In 1 year in 10 it comes by September 7.
What hardiness zone is 59820?
ZIP 59820 is in USDA zone 5b (-15 to -10°F average coldest winter night), per the 2023 USDA Plant Hardiness Zone Map ZIP listing.
What is the soil temperature in 59820 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
59804 Orchard Homes 59847 Lolo 59846 Huson 59872 Riverbend 59834 Frenchtown 59808 Missoula 59831 Dixon 59801 Missoula
Other ZIP codes in Mineral County
59830 59842 59866 59867 59872 All Mineral 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.