Last frost date in Nampa, ID

Average last frost
April 29

Expect the last frost in Nampa around April 29. Frost after May 18 happens in only one year out of ten. The first fall frost usually arrives about October 13, which leaves 164 frost-free days. An early freeze before September 29 happens one year in ten.

Safe after (10% risk)
May 18
Average first frost
Oct 13
Frost-free season
164 days
Hard freeze (28°F) ends
Apr 11
Next 7 nights in Nampa

No frost in the next 7 nights

Later than usual: the average first frost here is October 13.

National Weather Service forecast, updated Oct 22, 12:57 UTC

  1. ThuOct 2246°
  2. FriOct 2337°
  3. SatOct 2437°
  4. SunOct 2539°
  5. MonOct 2638°
  6. TueOct 2737°
  7. WedOct 2838°
JanFebMarAprMayJunJulAugSepOctNovDecLast frost Apr 29First frost Oct 13164 frost-free daysBlue: chance of 32°F frost. Green: average frost-free season.JFMAMJJASOND164 frost-free days
Frost risk through the year at Nampa Sugar Factory, 1.3 miles from Nampa.

Planting calendar for Nampa

Windows count forward or back from the average frost dates above. Click a crop for dates across Idaho.

Start indoorsPlant outSow outdoorsFall plantingAverage last and first frost
Warm-season crops
JanFebMarAprMayJunJulAugSepOctNovDec
TomatoesMay 6–May 20
PumpkinsMay 13–May 27
SunflowersApr 29–May 20
CucumbersMay 13–May 20
CornMay 6–May 20
Sweet potatoesMay 20–Jun 3
WatermelonMay 13–May 27
Green beansMay 6–May 27
ZucchiniMay 6–May 20
OkraMay 20–Jun 3
PeppersMay 13–May 27
BasilMay 6–May 20
Butternut squashMay 6–May 20
CantaloupeMay 13–May 27
EggplantMay 13–May 27
Cool-season crops
JanFebMarAprMayJunJulAugSepOctNovDec
PotatoesApr 1–Apr 15
OnionsMar 18–Apr 8
CarrotsApr 8–May 13
LettuceApr 15–May 6
BroccoliApr 1–Apr 15
BeetsApr 1–May 13
PeasMar 18–Apr 1
CabbageApr 1–Apr 15
RadishesMar 25–May 6
Brussels sproutsApr 15–Apr 29
SpinachMar 18–Apr 8
CilantroApr 15–May 6
KaleApr 1–Apr 15
Collard greensApr 1–Apr 15
TurnipsApr 1–Apr 15
DillApr 29–May 13
CeleryMay 6–May 13
CauliflowerApr 15–Apr 29
LeeksApr 15–Apr 29
Swiss chardApr 15–May 13
ParsleyApr 15–May 6
Fall bulbs and garlic
JanFebMarAprMayJunJulAugSepOctNovDec
Tulip bulbsSep 29–Nov 3
GarlicSep 22–Oct 27
Daffodil bulbsSep 15–Oct 27
Perennials
JanFebMarAprMayJunJulAugSepOctNovDec
StrawberriesApr 1–Apr 15
AsparagusApr 1–Apr 15

Frost probabilities

ThresholdSpring, 90% chance laterSpring, 50%Spring, 10%Fall, 10% chance earlierFall, 50%Fall, 90%
Light frost, 32°FApr 15Apr 29May 18Sep 29Oct 13Oct 28
Hard freeze, 28°FMar 25Apr 11May 1Oct 9Oct 25Nov 10

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 Nampa Sugar Factory (USC00106305) sits 1.3 miles from the center of Nampa at 2,470 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 Nampa, ID?

The average last frost date in Nampa is April 29, based on NOAA 1991–2020 climate normals. There is a 10% chance of frost after May 18.

When is the first frost in Nampa?

The first frost in fall usually comes around October 13. One year in ten it arrives before September 29.

How long is the growing season in Nampa?

About 164 days between the average last and first frost.

When should I plant tomatoes in Nampa?

Plant tomato seedlings outside from May 6 to May 20. Start seeds indoors six to eight weeks earlier.

Nearby in Idaho

All 16 cities in Idaho