Frost dates for American Falls, ID
When the last spring frost and first fall frost usually come, and when to plant, from 30 years of NOAA weather records.
Last spring frost
May 20
typical year
Safe to plant
June 9
frost is over in 9 of 10 years
First fall frost
September 26
typical year
Growing season
125 days
frost-free, typical year
Frost watch this week
Tonight's and the next six nights' lows from the National Weather Service forecast for the station's location. Frost: 32°F or colder. Possible frost: 33–36°F, mostly in low spots on clear, still nights.
When to plant
Counted from this page's frost dates. Warm-season crops wait for the safe-to-plant date.
| Crop | Start indoors | Plant outside | Fall planting |
|---|---|---|---|
| Cool-season crops | |||
| Peas | – | Apr 22 – May 6 | – |
| Spinach | – | Apr 8 – 29 | Aug 1 – 15 |
| Lettuce | – | Apr 22 – May 13 | Aug 1 – 15 |
| Radishes | – | Apr 22 – Jun 3 | Aug 15 – 29 |
| Onions | – | Apr 22 – May 6 | – |
| Potatoes | – | Apr 29 – May 13 | – |
| Carrots | – | Apr 29 – May 20 | Jul 4 – 18 |
| Beets | – | Apr 22 – May 6 | Jul 18 – Aug 1 |
| Kale | Mar 11 – 25 | Apr 22 – May 6 | Jul 18 – Aug 1 |
| Broccoli | Mar 11 – 25 | May 6 – 20 | Jul 18 – Aug 1 |
| Cabbage | Feb 25 – Mar 11 | Apr 22 – May 6 | Jul 18 – Aug 1 |
| Garlic | – | – | Aug 15 – Sep 5 |
| Warm-season crops | |||
| Tomatoes | Apr 14 – 28 | Jun 9 – 23 | – |
| Peppers | Apr 7 – 21 | Jun 16 – 30 | – |
| Cucumbers | – | Jun 9 – 30 | – |
| Zucchini | – | Jun 9 – Jul 7 | – |
| Pumpkins | – | Jun 9 – 30 | – |
| Green beans | – | Jun 9 – Jul 18 | – |
| Sweet corn | – | Jun 9 – Jul 7 | – |
| Basil | May 5 – 19 | Jun 16 – 23 | – |
Onions: from sets. Green beans: until 10 weeks before the first fall frost. Garlic: harvest next summer.
The year at a glance
Start indoors Plant outside Fall planting
The chance of frost, by date
| 1 year in 10 | Half of years | 9 years in 10 | |
|---|---|---|---|
| Spring frost after | June 9 | May 20 | May 4 |
| Fall frost before | September 8 | September 26 | October 11 |
Frost here means 32°F or colder. Read across: in 1 year in 10, spring frost carries on past the first date, which is why that date is the safe-to-plant date.
Hard freeze (28°F)
A hard freeze kills most garden plants, even hardy ones. The last one in spring usually comes around May 4 (May 19 in a late year), and the first one in fall around October 9.
Towns that use these dates
This is the nearest NOAA station with frost records for 2 towns.
American Falls, Rockland
Where these dates come from
NOAA weather station MASSACRE ROCKS SP, ID US (USC00105678), 1991–2020 climate normals. It's the nearest station for 2 zip codes, all within 16 miles:
83211, 83271
Planting dates follow common university extension advice; your local extension service can fine-tune them for your soil and microclimate.