Irwin, ID frost dates
Last spring frostAny monthno frost-free season
Freezing nights198 / yrat or below 32°F
Hardiness zone6aZone 6a
Gardening where frost is possible all year
The weather station nearest Irwin, ID records freezing temperatures in every month often enough that NOAA cannot define a frost-free season. Gardening is still possible — it just means planning for frost at any time:
- Grow fast, cold-tolerant crops: Radishes, Lettuce, Spinach, Kale, Peas, Potatoes, Swiss Chard, Garlic.
- Plant once the soil can be worked — usually late spring to early summer at high elevation — and keep row covers ready for clear, still nights.
- Use season extension: cold frames, low tunnels, wall-of-water cloches or a greenhouse turn a few frost-free weeks into a real season.
- Frost-tender crops (tomatoes, squash, beans) need protection all season; choose the earliest varieties you can find.
How Irwin compares
- Nearby Idaho Falls, ID, 62 km away, has a regular frost season (last frost May 9), a reminder of how much elevation and distance from the coast matter.
About these dates
Based on 1991–2020 NOAA climate normals for the Swan Valley, ID weather station, 6 km away (elevation 5,397 ft (1,645 m)).
Frost dates near Irwin
- Swan Valley frost any month
- Ririe frost any month
- Victor Jun 13 · Sep 9
- Driggs Jun 13 · Sep 9
- Wayan frost any month
- Tetonia Jun 13 · Sep 9
- Felt Jun 15 · Sep 7
- Iona May 9 · Oct 1
- Rigby May 9 · Oct 5
- Ucon May 9 · Oct 5
Frequently asked questions
When is the last frost in Irwin, ID?
Irwin, ID can freeze in any month, so there is no reliable last frost date. The nearest NOAA station averages 198 nights a year at or below 32°F.
What can I grow in Irwin, ID?
Fast, cold-tolerant crops such as radishes, lettuce, spinach, kale, peas and potatoes, ideally under row covers, cold frames or a greenhouse. Frost-tender crops like tomatoes need protection all season.