When to plant in Ammon, ID
USDA Zone 5bEverything below — frost dates, hardiness zone, and what to plant when in Ammon, Idaho — is derived from the closest NOAA station with complete climate normals.
In zone 5b, Ammon gardeners can grow many hardy perennials, while the last and first frost still dictate the annual vegetable calendar.
The average last spring frost in Ammon is now 8 days earlier than in the 1981–2010 normals. See how frost dates are shifting nationwide →
Frost probability
IDAHO FALLS - KIFI · 1991–2020The date the last spring and first fall frost occur, by threshold and probability. A 90% date is later in spring — and earlier in fall — than a 10% date; the 50% · 32°F row is what most gardeners plan around. These are Ammon’s own odds, recorded at IDAHO FALLS - KIFI.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | Jun 16 | May 30 | May 10 | Sep 4 | Sep 20 | Oct 3 |
| 32°F | Jun 2 | May 9 | Apr 27 | Sep 17 | Oct 1 | Oct 15 |
| 28°F | May 11 | Apr 28 | Apr 11 | Sep 27 | Oct 13 | Oct 27 |
Download this table as CSV ↓ — every threshold and probability, plus this city’s planting-window dates.
What to plant now
TODAY · JULY 19Full-year planting calendar
Each bar is the exact window to take a planting action in Ammon, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 20 km · complete 32°F normalsWhen stations disagree by more than a few days, that spread is real microclimate variation — elevation, water, urban heat. Judge which station best matches your own yard.
Ammon planting FAQ
When is the last spring frost in Ammon, ID?
On average, the last spring frost in Ammon is around May 9 (50% probability at 32°F, from 1991–2020 NOAA normals). Wait until after this date to set out tender plants like tomatoes and peppers.
When is the first fall frost in Ammon, ID?
The first fall frost in Ammon typically arrives around October 1 (50% probability at 32°F). Harvest or protect frost-sensitive crops before then.
What hardiness zone is Ammon in?
Ammon is in USDA hardiness zone 5b. In zone 5b, winters are cold — pick cold-hardy varieties and protect tender crops.
How long is the growing season in Ammon?
Ammon has about 145 frost-free days — a short growing season — between the average last spring frost (May 9) and first fall frost (October 1).
When should I plant tomatoes in Ammon?
For Ammon, sow tomatoes indoors about March 14–March 28 and move the seedlings out around May 16, after the last spring frost.
Never miss a window in Ammon
An email when it’s time to start seeds, transplant, and sow — timed to Ammon’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Idaho Falls · 6 km
- Rexburg · 41 km
- Blackfoot · 44 km
- Chubbuck · 73 km
- Pocatello · 79 km
- Jackson · 96 km
- Burley · 182 km
- Smithfield · 183 km
Frost dates recorded at IDAHO FALLS - KIFI, 6 km from the city center · 1991–2020 NOAA climate normals · zone from the USDA/PRISM 2023 map. How we compute this.
BlissGarden. "When to Plant in Ammon, ID — Frost Dates & Zone 5b." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00104455. Retrieved from https://blissgarden.com/idaho/ammon.