Last frost date in Idaho Falls, ID
The average last frost in Idaho Falls is May 9. By June 2 the chance of another 32°F night drops to 1 in 10. The first fall frost usually arrives about October 1, which leaves 142 frost-free days. An early freeze before September 17 happens one year in ten.
- Safe after (10% risk)
- Jun 2
- Average first frost
- Oct 1
- Frost-free season
- 142 days
- Hard freeze (28°F) ends
- Apr 28
Frost likely Sat night, low 31°F
National Weather Service forecast, updated Oct 22, 12:57 UTC
- ThuOct 2244°
- FriOct 2335°possible frost
- SatOct 2431°frost
- SunOct 2532°frost
- MonOct 2632°frost
- TueOct 2732°frost
- WedOct 2832°frost
Planting calendar for Idaho Falls
Windows count forward or back from the average frost dates above. Click a crop for dates across Idaho.
TomatoesMay 16–May 30
PumpkinsMay 23–Jun 6
SunflowersMay 9–May 30
CucumbersMay 23–May 30
CornMay 16–May 30
Sweet potatoesMay 30–Jun 13
WatermelonMay 23–Jun 6
Green beansMay 16–Jun 6
ZucchiniMay 16–May 30
OkraMay 30–Jun 13
PeppersMay 23–Jun 6
BasilMay 16–May 30
Butternut squashMay 16–May 30
CantaloupeMay 23–Jun 6
EggplantMay 23–Jun 6
PotatoesApr 11–Apr 25
OnionsMar 28–Apr 18
CarrotsApr 18–May 23
LettuceApr 25–May 16
BroccoliApr 11–Apr 25
BeetsApr 11–May 23
PeasMar 28–Apr 11
CabbageApr 11–Apr 25
RadishesApr 4–May 16
Brussels sproutsApr 25–May 9
SpinachMar 28–Apr 18
CilantroApr 25–May 16
KaleApr 11–Apr 25
Collard greensApr 11–Apr 25
TurnipsApr 11–Apr 25
DillMay 9–May 23
CeleryMay 16–May 23
CauliflowerApr 25–May 9
LeeksApr 25–May 9
Swiss chardApr 25–May 23
ParsleyApr 25–May 16
Tulip bulbsSep 17–Oct 22
GarlicSep 10–Oct 15
Daffodil bulbsSep 3–Oct 15
StrawberriesApr 11–Apr 25
AsparagusApr 11–Apr 25Frost probabilities
| Threshold | Spring, 90% chance later | Spring, 50% | Spring, 10% | Fall, 10% chance earlier | Fall, 50% | Fall, 90% |
|---|---|---|---|---|---|---|
| Light frost, 32°F | Apr 27 | May 9 | Jun 2 | Sep 17 | Oct 1 | Oct 15 |
| Hard freeze, 28°F | Apr 11 | Apr 28 | May 11 | Sep 27 | Oct 13 | Oct 27 |
Read the spring 10% column as the date after which only one year in ten still gets frost. That is the safer date for tomatoes, peppers and basil.
Where these numbers come from
NOAA station Idaho Falls - Kifi (USC00104455) sits 2.0 miles from the center of Idaho Falls at 4,742 feet. Its averages cover 1991 to 2020. Low spots, valleys and open fields can keep getting frost a week or two after the station stops; city centers and lakeshores usually get less of it.
Questions
When is the last frost in Idaho Falls, ID?
The average last frost date in Idaho Falls is May 9, based on NOAA 1991–2020 climate normals. There is a 10% chance of frost after June 2.
When is the first frost in Idaho Falls?
The first frost in fall usually comes around October 1. One year in ten it arrives before September 17.
How long is the growing season in Idaho Falls?
About 142 days between the average last and first frost.
When should I plant tomatoes in Idaho Falls?
Plant tomato seedlings outside from May 16 to May 30. Start seeds indoors six to eight weeks earlier.