Fall in zone 5aPhoto: Dietmar Rabich, CC BY-SA 4.0, via Wikimedia Commons
Frost dates for ZIP 82420 (Cowley, WY)
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, Lovell, WY (6 miles away).
- Average last spring frostMay 950% chance of a 32°F freeze after this date
- Average first fall frostSep 2950% chance of a 32°F freeze by this date
- Growing season (frost-free)142 daysmedian, 32°F threshold
- USDA hardiness zone5a-20 to -15°F avg. coldest night
Get The Dial for 82420 (Cowley)
Frost and freeze alerts from the NWS forecast for 82420, the spring soil-temperature heads-up for pre-emergent, and a short weekly yard-timing email.
- Freeze alerts
- Soil-temp heads-up
- Weekly yard to-dos
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.
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 82420 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) | Apr 27 |
| 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 16 |
| 50% (the "average" first frost) | Sep 29 |
| 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 22 | Sep 19 |
| 32°F (freeze) | May 9 | Sep 29 |
| 28°F (hard freeze) | Apr 29 | Oct 9 |
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 82420
Dates count from your average last spring frost (May 9) and first fall frost (Sep 29). 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 4–25 (transplant) Jul 21–Aug 18 (sowing) |
| Spinach | – | Mar 28–Apr 18 (sow outdoors) | Aug 4–25 (sowing) |
| Kale | Mar 14–28 | Apr 11–25 (transplant) Apr 11–25 (sow outdoors) | Jul 7–Aug 4 (transplant) Jun 23–Jul 21 (sowing) |
| Collards | Mar 14–28 | Apr 11–May 9 (transplant) Apr 11–May 9 (sow outdoors) | Jul 7–Aug 4 (transplant) Jun 23–Jul 21 (sowing) |
| Broccoli | Feb 28–Mar 14 | Apr 11–25 (transplant) | Jun 23–Jul 21 (transplant) |
| Cabbage | Feb 28–Mar 14 | Apr 11–25 (transplant) | Jun 23–Jul 21 (transplant) |
| Cauliflower | Feb 28–Mar 14 | Apr 25–May 9 (transplant) | Jun 23–Jul 21 (transplant) |
| Brussels sprouts | Feb 14–28 | Apr 11–25 (transplant) | Jun 9–30 (transplant) |
| Kohlrabi | Mar 14–28 | Apr 11–25 (transplant) Apr 11–25 (sow outdoors) | Jul 21–Aug 4 (sowing) |
| Bok choy / Asian greens | – | Apr 11–25 (sow outdoors) | Aug 4–18 (sowing) |
| Arugula | – | Apr 11–May 9 (sow outdoors) | Aug 4–Sep 1 (sowing) |
| Mustard greens | – | Apr 11–May 2 (sow outdoors) | Aug 4–18 (sowing) |
| Swiss chard | Mar 28–Apr 11 | Apr 25–May 16 (transplant) Apr 25–May 23 (sow outdoors) | Jul 21–Aug 4 (sowing) |
| Beet | – | Apr 11–May 9 (sow outdoors) | Jul 21–Aug 4 (sowing) |
| Carrot | – | Apr 18–May 16 (sow outdoors) | Jul 7–21 (sowing) |
| Radish | – | Apr 4–May 16 (sow outdoors) | Aug 18–Sep 1 (sowing) |
| Turnip | – | Apr 11–May 2 (sow outdoors) | Jul 21–Aug 4 (sowing) |
| Parsnip | – | Apr 18–May 9 (sow outdoors) | – |
| Pea (garden, snap, snow) | – | Mar 14–Apr 11 (sow outdoors) | Jul 7–21 (sowing) |
| Onion (bulbing) | Feb 14–28 | Mar 28–Apr 11 (transplant) | – |
| Green onion / scallion | – | Mar 28–Apr 25 (sow outdoors) | Jul 21–Aug 4 (sowing) |
| Leek | Feb 14–28 | Apr 11–25 (transplant) | – |
| Garlic | – | – | Aug 18–Sep 15 (sowing) |
| Shallot | – | Mar 28–Apr 11 (transplant) | Aug 18–Sep 15 (sowing) |
| Potato | – | Apr 11–25 (transplant) | Jun 9–23 (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 4–18 (sowing) |
| Parsley | Feb 28–Mar 14 | Apr 25–May 9 (transplant) Apr 18–May 9 (sow outdoors) | – |
| Dill | – | May 9–23 (sow outdoors) | Aug 4–18 (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 21–Aug 18 (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: Lovell, WY (NOAA GHCN-Daily ID USC00485770), elevation 3,847 ft, 6.3 miles from the ZIP's center point. NOAA completeness flag: S (standard, 24+ years).
Nearby stations
| Station | Distance | Last frost (50%) | First frost (50%) |
|---|---|---|---|
| Deaver, WY | 7 mi | May 6 | Oct 1 |
| Powell Fld STN, WY | 17 mi | May 19 | Sep 20 |
| Heart Mtn, WY | 28 mi | May 15 | Sep 25 |
The average last-frost dates of these stations span 13 days, a rough guide to local variation. See data sources & methods.
Frost questions for 82420
When is the last frost in 82420?
The average (50% chance) last spring freeze of 32°F for ZIP 82420 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 82420?
The average first fall freeze is September 29. In 1 year in 10 it comes by September 16.
What hardiness zone is 82420?
ZIP 82420 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 82420 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
82421 Deaver 82423 Frannie 82412 Byron 82431 Lovell 59014 Bridger 82440 Ralston 59066 Pryor 82422
Other ZIP codes in Big Horn County
82410 82411 82412 82421 82422 82423 82426 82428 82431 82432 82434 82441 All Big Horn County frost dates · Wyoming frost dates
Never miss a frost: get The Dial
Weekly yard timing, plus frost and soil-temperature alerts for your ZIP code.
- Freeze alerts
- Soil-temp heads-up
- Weekly yard to-dos
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.