Fall in zone 5bPhoto: Dietmar Rabich, CC BY-SA 4.0, via Wikimedia Commons
Frost dates for ZIP 83427 (Iona, 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 Falls 16 SE, ID (2 miles away).
- Average last spring frostJun 950% chance of a 32°F freeze after this date
- Average first fall frostSep 1150% chance of a 32°F freeze by this date
- Growing season (frost-free)93 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
45°F Below 50°F
24-hour average · latest 42°F, as of Oct 18, 1:00 AM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Moose 1 NNE (56 mi).
4-inch depth
46°F Below 50°F
24-hour average · latest 46°F, as of Oct 18, 1:00 AM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Moose 1 NNE (56 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 83427 load here. You can also open the NWS forecast for this ZIP.
Pre-emergent
Soil is 46°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 19 |
| 50% (the "average" last frost) | Jun 9 |
| 10% (cautious: only 1 year in 10 freezes later) | Jun 26 |
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 27 |
| 50% (the "average" first frost) | Sep 11 |
| 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 9 | Sep 11 |
| 28°F (hard freeze) | May 19 | Sep 23 |
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 83427
Dates count from your average last spring frost (Jun 9) and first fall frost (Sep 11). 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 14–28 | Jun 16–30 (transplant) | – |
| Pepper (sweet and hot) | Mar 31–Apr 14 | Jun 23–Jul 7 (transplant) | – |
| Eggplant | Mar 31–Apr 14 | Jun 23–Jul 7 (transplant) | – |
| Tomatillo | Apr 14–28 | Jun 16–30 (transplant) | – |
| Lettuce | Apr 14–28 | May 19–Jun 9 (transplant) May 12–Jun 23 (sow outdoors) | Jul 17–Aug 7 (transplant) Jul 3–31 (sowing) |
| Spinach | – | Apr 28–May 19 (sow outdoors) | Jul 17–Aug 7 (sowing) |
| Kale | Apr 14–28 | May 12–26 (transplant) May 12–26 (sow outdoors) | Jun 19–Jul 17 (transplant) Jun 5–Jul 3 (sowing) |
| Collards | Apr 14–28 | May 12–Jun 9 (transplant) May 12–Jun 9 (sow outdoors) | Jun 19–Jul 17 (transplant) |
| Broccoli | Mar 31–Apr 14 | May 12–26 (transplant) | Jun 5–Jul 3 (transplant) |
| Cabbage | Mar 31–Apr 14 | May 12–26 (transplant) | Jun 5–Jul 3 (transplant) |
| Cauliflower | Mar 31–Apr 14 | May 26–Jun 9 (transplant) | – |
| Brussels sprouts | Mar 17–31 | May 12–26 (transplant) | – |
| Kohlrabi | Apr 14–28 | May 12–26 (transplant) May 12–26 (sow outdoors) | Jul 3–17 (sowing) |
| Bok choy / Asian greens | – | May 12–26 (sow outdoors) | Jul 17–31 (sowing) |
| Arugula | – | May 12–Jun 9 (sow outdoors) | Jul 17–Aug 14 (sowing) |
| Mustard greens | – | May 12–Jun 2 (sow outdoors) | Jul 17–31 (sowing) |
| Swiss chard | Apr 28–May 12 | May 26–Jun 16 (transplant) May 26–Jun 23 (sow outdoors) | Jul 3–17 (sowing) |
| Beet | – | May 12–Jun 9 (sow outdoors) | Jul 3–17 (sowing) |
| Carrot | – | May 19–Jun 16 (sow outdoors) | Jun 19–Jul 3 (sowing) |
| Radish | – | May 5–Jun 16 (sow outdoors) | Jul 31–Aug 14 (sowing) |
| Turnip | – | May 12–Jun 2 (sow outdoors) | Jul 3–17 (sowing) |
| Parsnip | – | May 19–Jun 9 (sow outdoors) | – |
| Pea (garden, snap, snow) | – | Apr 14–May 12 (sow outdoors) | Jun 19–Jul 3 (sowing) |
| Onion (bulbing) | Mar 17–31 | Apr 28–May 12 (transplant) | – |
| Green onion / scallion | – | Apr 28–May 26 (sow outdoors) | Jul 3–17 (sowing) |
| Leek | Mar 17–31 | May 12–26 (transplant) | – |
| Garlic | – | – | Jul 31–Aug 28 (sowing) |
| Shallot | – | Apr 28–May 12 (transplant) | Jul 31–Aug 28 (sowing) |
| Potato | – | May 12–26 (transplant) | – |
| Sweet potato | – | Jun 30–Jul 14 (transplant) | – |
| Sweet corn | – | Jun 16–30 (sow outdoors) | – |
| Bean, bush (snap) | – | Jun 16–30 (sow outdoors) | – |
| Bean, pole | – | Jun 16–30 (sow outdoors) | – |
| Lima bean | – | Jun 23–Jul 7 (sow outdoors) | – |
| Southern pea (cowpea, black-eyed pea) | – | Jun 30–Jul 21 (sow outdoors) | – |
| Cucumber | May 12–19 | Jun 16–30 (transplant) Jun 16–30 (sow outdoors) | – |
| Summer squash / zucchini | May 12–19 | Jun 16–30 (transplant) Jun 16–30 (sow outdoors) | – |
| Winter squash | May 12–19 | Jun 16–30 (transplant) Jun 16–30 (sow outdoors) | – |
| Pumpkin | – | Jun 16–30 (sow outdoors) | – |
| Watermelon | May 12–19 | Jun 23–Jul 7 (transplant) Jun 23–Jul 7 (sow outdoors) | – |
| Cantaloupe / muskmelon | May 12–19 | Jun 23–Jul 7 (transplant) Jun 23–Jul 7 (sow outdoors) | – |
| Okra | Apr 28–May 12 | Jun 23–Jul 7 (transplant) Jun 23–Jul 7 (sow outdoors) | – |
| Celery | Mar 17–31 | Jun 16–23 (transplant) | – |
| Basil | Apr 28–May 12 | Jun 16–30 (transplant) Jun 16–30 (sow outdoors) | – |
| Cilantro | – | May 26–Jun 23 (sow outdoors) | Jul 17–31 (sowing) |
| Parsley | Mar 31–Apr 14 | May 26–Jun 9 (transplant) May 19–Jun 9 (sow outdoors) | – |
| Dill | – | Jun 9–23 (sow outdoors) | Jul 17–31 (sowing) |
| Sunflower | – | Jun 9–23 (sow outdoors) | – |
| Asparagus (crowns) | – | May 12–26 (transplant) | – |
| Rhubarb (crowns) | – | May 12–26 (transplant) | – |
| Strawberry (plants) | – | May 12–26 (transplant) | Jul 3–31 (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 Falls 16 SE, ID (NOAA GHCN-Daily ID USC00104456), elevation 5,828 ft, 1.7 miles from the ZIP's center point. NOAA completeness flag: R (representative, 10+ years).
Nearby stations
| Station | Distance | Last frost (50%) | First frost (50%) |
|---|---|---|---|
| Idaho Falls - Kifi, ID | 17 mi | May 9 | Oct 1 |
| Idaho Falls Fanning Fld, ID | 19 mi | May 23 | Sep 20 |
| Rigby, ID | 23 mi | May 9 | Oct 5 |
The average last-frost dates of these stations span 31 days, a rough guide to local variation. See data sources & methods.
Frost questions for 83427
When is the last frost in 83427?
The average (50% chance) last spring freeze of 32°F for ZIP 83427 is June 9. For a more cautious planting date, use June 26, when only 1 year in 10 still sees a later freeze.
When is the first frost in 83427?
The average first fall freeze is September 11. In 1 year in 10 it comes by August 27.
What hardiness zone is 83427?
ZIP 83427 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 83427 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
83406 Ammon 83236 Firth 83404 Idaho Falls 83401 Lincoln 83443 Ririe 83274 Shelley 83442 Rigby 83454 Ucon
Other ZIP codes in Bonneville County
83120 83285 83401 83402 83404 83406 83428 83443 83449 83454 All Bonneville County frost dates · Idaho 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.