Frost dates for ZIP 83631 (Idaho City, ID)
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, Idaho City, ID (4 miles away).
- Average last spring frostJun 1750% chance of a 32°F freeze after this date
- Average first fall frostSep 550% chance of a 32°F freeze by this date
- Growing season (frost-free)80 daysmedian, 32°F threshold
- USDA hardiness zone6b-5 to 0°F avg. coldest night
This week in your yard
As of Oct 18, 2026, from your frost dates, zone and soil temperature. Lawn timing · Vegetables · Pruning · Plants
Fall in zone 6b
Soil temperature now
2-inch depth
60°F 55°F or warmer
24-hour average · latest 51°F, as of Oct 18, 8:00 AM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Orchard Range Site (40 mi).
4-inch depth
60°F 55°F or warmer
24-hour average · latest 57°F, as of Oct 18, 8:00 AM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Orchard Range Site (40 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 83631 load here. You can also open the NWS forecast for this ZIP.
Pre-emergent
Soil is 60°F at 4 inches (estimated soil temperature, not a station reading). Fall pre-emergent (annual bluegrass, winter weeds): window open as soil cools through the 70s and 60s.
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 30 |
| 50% (the "average" last frost) | Jun 17 |
| 10% (cautious: only 1 year in 10 freezes later) | Jul 4 |
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 23 |
| 50% (the "average" first frost) | Sep 5 |
| 90% (late: most years have frozen by now) | Sep 21 |
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 17 | Sep 5 |
| 28°F (hard freeze) | May 22 | Sep 19 |
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 83631
Dates count from your average last spring frost (Jun 17) and first fall frost (Sep 5). 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 22–May 6 | Jun 24–Jul 8 (transplant) | – |
| Pepper (sweet and hot) | Apr 8–22 | Jul 1–15 (transplant) | – |
| Eggplant | Apr 8–22 | Jul 1–15 (transplant) | – |
| Tomatillo | Apr 22–May 6 | Jun 24–Jul 8 (transplant) | – |
| Lettuce | Apr 22–May 6 | May 27–Jun 17 (transplant) May 20–Jul 1 (sow outdoors) | Jul 11–Aug 1 (transplant) |
| Spinach | – | May 6–27 (sow outdoors) | Jul 11–Aug 1 (sowing) |
| Kale | Apr 22–May 6 | May 20–Jun 3 (transplant) May 20–Jun 3 (sow outdoors) | Jun 13–Jul 11 (transplant) |
| Collards | Apr 22–May 6 | May 20–Jun 17 (transplant) May 20–Jun 17 (sow outdoors) | – |
| Broccoli | Apr 8–22 | May 20–Jun 3 (transplant) | – |
| Cabbage | Apr 8–22 | May 20–Jun 3 (transplant) | – |
| Cauliflower | Apr 8–22 | Jun 3–17 (transplant) | – |
| Brussels sprouts | Mar 25–Apr 8 | May 20–Jun 3 (transplant) | – |
| Kohlrabi | Apr 22–May 6 | May 20–Jun 3 (transplant) May 20–Jun 3 (sow outdoors) | Jun 27–Jul 11 (sowing) |
| Bok choy / Asian greens | – | May 20–Jun 3 (sow outdoors) | Jul 11–25 (sowing) |
| Arugula | – | May 20–Jun 17 (sow outdoors) | Jul 11–Aug 8 (sowing) |
| Mustard greens | – | May 20–Jun 10 (sow outdoors) | Jul 11–25 (sowing) |
| Swiss chard | May 6–20 | Jun 3–24 (transplant) Jun 3–Jul 1 (sow outdoors) | – |
| Beet | – | May 20–Jun 17 (sow outdoors) | Jun 27–Jul 11 (sowing) |
| Carrot | – | May 27–Jun 24 (sow outdoors) | – |
| Radish | – | May 13–Jun 24 (sow outdoors) | Jul 25–Aug 8 (sowing) |
| Turnip | – | May 20–Jun 10 (sow outdoors) | Jun 27–Jul 11 (sowing) |
| Parsnip | – | May 27–Jun 17 (sow outdoors) | – |
| Pea (garden, snap, snow) | – | Apr 22–May 20 (sow outdoors) | Jun 13–27 (sowing) |
| Onion (bulbing) | Mar 25–Apr 8 | May 6–20 (transplant) | – |
| Green onion / scallion | – | May 6–Jun 3 (sow outdoors) | Jun 27–Jul 11 (sowing) |
| Leek | Mar 25–Apr 8 | May 20–Jun 3 (transplant) | – |
| Garlic | – | – | Jul 25–Aug 22 (sowing) |
| Shallot | – | May 6–20 (transplant) | Jul 25–Aug 22 (sowing) |
| Potato | – | May 20–Jun 3 (transplant) | – |
| Sweet potato | – | Jul 8–22 (transplant) | – |
| Sweet corn | – | Jun 24–Jul 8 (sow outdoors) | – |
| Bean, bush (snap) | – | Jun 24–Jul 8 (sow outdoors) | – |
| Bean, pole | – | Jun 24–Jul 8 (sow outdoors) | – |
| Lima bean | – | Jul 1–15 (sow outdoors) | – |
| Southern pea (cowpea, black-eyed pea) | – | Jul 8–29 (sow outdoors) | – |
| Cucumber | May 20–27 | Jun 24–Jul 8 (transplant) Jun 24–Jul 8 (sow outdoors) | – |
| Summer squash / zucchini | May 20–27 | Jun 24–Jul 8 (transplant) Jun 24–Jul 8 (sow outdoors) | – |
| Winter squash | May 20–27 | Jun 24–Jul 8 (transplant) Jun 24–Jul 8 (sow outdoors) | – |
| Pumpkin | – | Jun 24–Jul 8 (sow outdoors) | – |
| Watermelon | May 20–27 | Jul 1–15 (transplant) Jul 1–15 (sow outdoors) | – |
| Cantaloupe / muskmelon | May 20–27 | Jul 1–15 (transplant) Jul 1–15 (sow outdoors) | – |
| Okra | May 6–20 | Jul 1–15 (transplant) Jul 1–15 (sow outdoors) | – |
| Celery | Mar 25–Apr 8 | Jun 24–Jul 1 (transplant) | – |
| Basil | May 6–20 | Jun 24–Jul 8 (transplant) Jun 24–Jul 8 (sow outdoors) | – |
| Cilantro | – | Jun 3–Jul 1 (sow outdoors) | Jul 11–25 (sowing) |
| Parsley | Apr 8–22 | Jun 3–17 (transplant) May 27–Jun 17 (sow outdoors) | – |
| Dill | – | Jun 17–Jul 1 (sow outdoors) | Jul 11–25 (sowing) |
| Sunflower | – | Jun 17–Jul 1 (sow outdoors) | – |
| Asparagus (crowns) | – | May 20–Jun 3 (transplant) | – |
| Rhubarb (crowns) | – | May 20–Jun 3 (transplant) | – |
| Strawberry (plants) | – | May 20–Jun 3 (transplant) | Jun 27–Jul 25 (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: Idaho City, ID (NOAA GHCN-Daily ID USC00104442), elevation 3,965 ft, 4.2 miles from the ZIP's center point. NOAA completeness flag: R (representative, 10+ years).
Nearby stations
| Station | Distance | Last frost (50%) | First frost (50%) |
|---|---|---|---|
| Lowman, ID | 16 mi | Jun 6 | Sep 4 |
| Garden Valley, ID | 18 mi | Jun 1 | Sep 10 |
| Arrowrock Dam, ID | 21 mi | Apr 28 | Oct 14 |
The average last-frost dates of these stations span 51 days, a rough guide to local variation. See data sources & methods.
Frost questions for 83631
When is the last frost in 83631?
The average (50% chance) last spring freeze of 32°F for ZIP 83631 is June 17. For a more cautious planting date, use July 4, when only 1 year in 10 still sees a later freeze.
When is the first frost in 83631?
The average first fall freeze is September 5. In 1 year in 10 it comes by August 23.
What hardiness zone is 83631?
ZIP 83631 is in USDA zone 6b (-5 to 0°F average coldest winter night), per the 2023 USDA Plant Hardiness Zone Map ZIP listing.
What is the soil temperature in 83631 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
83666 Placerville 83622 Garden Valley 83629 Horseshoe Bend 83602 Banks 83702 Boise City 83712 Boise City 83703 Boise City 83714 Garden City
Other ZIP codes in Boise County
83602 83622 83629 83637 83666 All Boise County frost dates · Idaho frost dates
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