Fall in zone 4bPhoto: Dietmar Rabich, CC BY-SA 4.0, via Wikimedia Commons
Frost dates for ZIP 59636 (Helena West Side, 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, Helena Rgnl AP, MT (7 miles away).
- Average last spring frostMay 950% chance of a 32°F freeze after this date
- Average first fall frostSep 3050% chance of a 32°F freeze by this date
- Growing season (frost-free)142 daysmedian, 32°F threshold
- USDA hardiness zone4b-25 to -20°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
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 (62 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 (62 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 59636 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) | Apr 29 |
| 50% (the "average" last frost) | May 9 |
| 10% (cautious: only 1 year in 10 freezes later) | May 25 |
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 17 |
| 50% (the "average" first frost) | Sep 30 |
| 90% (late: most years have frozen by now) | Oct 11 |
Light frost, freeze and hard freeze
| Threshold | Last spring (50%) | First fall (50%) |
|---|---|---|
| 36°F (light frost possible on clear, calm nights) | May 25 | Sep 19 |
| 32°F (freeze) | May 9 | Sep 30 |
| 28°F (hard freeze) | Apr 29 | Oct 7 |
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 59636
Dates count from your average last spring frost (May 9) and first fall frost (Sep 30). 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 14–28 | May 16–30 (transplant) | – |
| Pepper (sweet and hot) | Feb 28–Mar 14 | May 23–Jun 6 (transplant) | – |
| Eggplant | Feb 28–Mar 14 | May 23–Jun 6 (transplant) | – |
| Tomatillo | Mar 14–28 | May 16–30 (transplant) | – |
| Lettuce | Mar 14–28 | Apr 18–May 9 (transplant) Apr 11–May 23 (sow outdoors) | Aug 5–26 (transplant) Jul 22–Aug 19 (sowing) |
| Spinach | – | Mar 28–Apr 18 (sow outdoors) | Aug 5–26 (sowing) |
| Kale | Mar 14–28 | Apr 11–25 (transplant) Apr 11–25 (sow outdoors) | Jul 8–Aug 5 (transplant) Jun 24–Jul 22 (sowing) |
| Collards | Mar 14–28 | Apr 11–May 9 (transplant) Apr 11–May 9 (sow outdoors) | Jul 8–Aug 5 (transplant) Jun 24–Jul 22 (sowing) |
| Broccoli | Feb 28–Mar 14 | Apr 11–25 (transplant) | Jun 24–Jul 22 (transplant) |
| Cabbage | Feb 28–Mar 14 | Apr 11–25 (transplant) | Jun 24–Jul 22 (transplant) |
| Cauliflower | Feb 28–Mar 14 | Apr 25–May 9 (transplant) | Jun 24–Jul 22 (transplant) |
| Brussels sprouts | Feb 14–28 | Apr 11–25 (transplant) | Jun 10–Jul 1 (transplant) |
| Kohlrabi | Mar 14–28 | Apr 11–25 (transplant) Apr 11–25 (sow outdoors) | Jul 22–Aug 5 (sowing) |
| Bok choy / Asian greens | – | Apr 11–25 (sow outdoors) | Aug 5–19 (sowing) |
| Arugula | – | Apr 11–May 9 (sow outdoors) | Aug 5–Sep 2 (sowing) |
| Mustard greens | – | Apr 11–May 2 (sow outdoors) | Aug 5–19 (sowing) |
| Swiss chard | Mar 28–Apr 11 | Apr 25–May 16 (transplant) Apr 25–May 23 (sow outdoors) | Jul 22–Aug 5 (sowing) |
| Beet | – | Apr 11–May 9 (sow outdoors) | Jul 22–Aug 5 (sowing) |
| Carrot | – | Apr 18–May 16 (sow outdoors) | Jul 8–22 (sowing) |
| Radish | – | Apr 4–May 16 (sow outdoors) | Aug 19–Sep 2 (sowing) |
| Turnip | – | Apr 11–May 2 (sow outdoors) | Jul 22–Aug 5 (sowing) |
| Parsnip | – | Apr 18–May 9 (sow outdoors) | – |
| Pea (garden, snap, snow) | – | Mar 14–Apr 11 (sow outdoors) | Jul 8–22 (sowing) |
| Onion (bulbing) | Feb 14–28 | Mar 28–Apr 11 (transplant) | – |
| Green onion / scallion | – | Mar 28–Apr 25 (sow outdoors) | Jul 22–Aug 5 (sowing) |
| Leek | Feb 14–28 | Apr 11–25 (transplant) | – |
| Garlic | – | – | Aug 19–Sep 16 (sowing) |
| Shallot | – | Mar 28–Apr 11 (transplant) | Aug 19–Sep 16 (sowing) |
| Potato | – | Apr 11–25 (transplant) | Jun 10–24 (transplant) |
| Sweet potato | – | May 30–Jun 13 (transplant) | – |
| Sweet corn | – | May 16–30 (sow outdoors) | – |
| Bean, bush (snap) | – | May 16–30 (sow outdoors) | – |
| Bean, pole | – | May 16–30 (sow outdoors) | – |
| Lima bean | – | May 23–Jun 6 (sow outdoors) | – |
| Southern pea (cowpea, black-eyed pea) | – | May 30–Jun 20 (sow outdoors) | – |
| Cucumber | Apr 11–18 | May 16–30 (transplant) May 16–30 (sow outdoors) | – |
| Summer squash / zucchini | Apr 11–18 | May 16–30 (transplant) May 16–30 (sow outdoors) | – |
| Winter squash | Apr 11–18 | May 16–30 (transplant) May 16–30 (sow outdoors) | – |
| Pumpkin | – | May 16–30 (sow outdoors) | – |
| Watermelon | Apr 11–18 | May 23–Jun 6 (transplant) May 23–Jun 6 (sow outdoors) | – |
| Cantaloupe / muskmelon | Apr 11–18 | May 23–Jun 6 (transplant) May 23–Jun 6 (sow outdoors) | – |
| Okra | Mar 28–Apr 11 | May 23–Jun 6 (transplant) May 23–Jun 6 (sow outdoors) | – |
| Celery | Feb 14–28 | May 16–23 (transplant) | – |
| Basil | Mar 28–Apr 11 | May 16–30 (transplant) May 16–30 (sow outdoors) | – |
| Cilantro | – | Apr 25–May 23 (sow outdoors) | Aug 5–19 (sowing) |
| Parsley | Feb 28–Mar 14 | Apr 25–May 9 (transplant) Apr 18–May 9 (sow outdoors) | – |
| Dill | – | May 9–23 (sow outdoors) | Aug 5–19 (sowing) |
| Sunflower | – | May 9–23 (sow outdoors) | – |
| Asparagus (crowns) | – | Apr 11–25 (transplant) | – |
| Rhubarb (crowns) | – | Apr 11–25 (transplant) | – |
| Strawberry (plants) | – | Apr 11–25 (transplant) | Jul 22–Aug 19 (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: Helena Rgnl AP, MT (NOAA GHCN-Daily ID USW00024144), elevation 3,828 ft, 7.1 miles from the ZIP's center point. NOAA completeness flag: S (standard, 24+ years).
Nearby stations
| Station | Distance | Last frost (50%) | First frost (50%) |
|---|---|---|---|
| Austin 1 W, MT | 7 mi | Jun 4 | Sep 14 |
| Elliston, MT | 16 mi | Jun 9 | Sep 8 |
| Tizer Gardens, MT | 17 mi | Jun 18 | Sep 5 |
The average last-frost dates of these stations span 40 days, a rough guide to local variation. See data sources & methods.
Frost questions for 59636
When is the last frost in 59636?
The average (50% chance) last spring freeze of 32°F for ZIP 59636 is May 9. For a more cautious planting date, use May 25, when only 1 year in 10 still sees a later freeze.
When is the first frost in 59636?
The average first fall freeze is September 30. In 1 year in 10 it comes by September 17.
What hardiness zone is 59636?
ZIP 59636 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 59636 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
59625 Helena 59623 Helena 59601 Helena 59602 Helena Valley Northeast 59634 Clancy 59635 Spokane Creek 59640 Marysville 59728 Elliston
Other ZIP codes in Lewis and Clark County
59410 59601 59602 59623 59625 59633 59635 59639 59640 59648 All Lewis and Clark County frost dates · Montana frost dates
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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.