Last frost date in Ottumwa, IA

Average last frost
April 23

Expect the last frost in Ottumwa around April 23. Frost after May 7 happens in only one year out of ten. The first fall frost usually arrives about October 14, which leaves 172 frost-free days. An early freeze before September 29 happens one year in ten.

Safe after (10% risk)
May 7
Average first frost
Oct 14
Frost-free season
172 days
Hard freeze (28°F) ends
Apr 13
Next 7 nights in Ottumwa

No frost in the next 7 nights

Later than usual: the average first frost here is October 14.

National Weather Service forecast, updated Oct 22, 12:24 UTC

  1. ThuOct 2252°
  2. FriOct 2355°
  3. SatOct 2454°
  4. SunOct 2554°
  5. MonOct 2649°
  6. TueOct 2745°
  7. WedOct 2847°
JanFebMarAprMayJunJulAugSepOctNovDecLast frost Apr 23First frost Oct 14172 frost-free daysBlue: chance of 32°F frost. Green: average frost-free season.JFMAMJJASOND172 frost-free days
Frost risk through the year at Ottumwa Industrial Airport, 6.0 miles from Ottumwa.

Planting calendar for Ottumwa

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

Start indoorsPlant outSow outdoorsFall plantingAverage last and first frost
Warm-season crops
JanFebMarAprMayJunJulAugSepOctNovDec
TomatoesApr 30–May 14
PumpkinsMay 7–May 21
SunflowersApr 23–May 14
CucumbersMay 7–May 14
CornApr 30–May 14
Sweet potatoesMay 14–May 28
WatermelonMay 7–May 21
Green beansApr 30–May 21
ZucchiniApr 30–May 14
OkraMay 14–May 28
PeppersMay 7–May 21
BasilApr 30–May 14
Butternut squashApr 30–May 14
CantaloupeMay 7–May 21
EggplantMay 7–May 21
Cool-season crops
JanFebMarAprMayJunJulAugSepOctNovDec
PotatoesMar 26–Apr 9
OnionsMar 12–Apr 2
CarrotsApr 2–May 7
LettuceApr 9–Apr 30
BroccoliMar 26–Apr 9
BeetsMar 26–May 7
PeasMar 12–Mar 26
CabbageMar 26–Apr 9
RadishesMar 19–Apr 30
Brussels sproutsApr 9–Apr 23
SpinachMar 12–Apr 2
CilantroApr 9–Apr 30
KaleMar 26–Apr 9
Collard greensMar 26–Apr 9
TurnipsMar 26–Apr 9
DillApr 23–May 7
CeleryApr 30–May 7
CauliflowerApr 9–Apr 23
LeeksApr 9–Apr 23
Swiss chardApr 9–May 7
ParsleyApr 9–Apr 30
Fall bulbs and garlic
JanFebMarAprMayJunJulAugSepOctNovDec
Tulip bulbsSep 30–Nov 4
GarlicSep 23–Oct 28
Daffodil bulbsSep 16–Oct 28
Perennials
JanFebMarAprMayJunJulAugSepOctNovDec
StrawberriesMar 26–Apr 9
AsparagusMar 26–Apr 9

Frost probabilities

ThresholdSpring, 90% chance laterSpring, 50%Spring, 10%Fall, 10% chance earlierFall, 50%Fall, 90%
Light frost, 32°FApr 9Apr 23May 7Sep 29Oct 14Oct 26
Hard freeze, 28°FApr 1Apr 13Apr 28Oct 10Oct 24Nov 5

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 Ottumwa Industrial Airport (USW00014950) sits 6.0 miles from the center of Ottumwa at 842 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 Ottumwa, IA?

The average last frost date in Ottumwa is April 23, based on NOAA 1991–2020 climate normals. There is a 10% chance of frost after May 7.

When is the first frost in Ottumwa?

The first frost in fall usually comes around October 14. One year in ten it arrives before September 29.

How long is the growing season in Ottumwa?

About 172 days between the average last and first frost.

When should I plant tomatoes in Ottumwa?

Plant tomato seedlings outside from April 30 to May 14. Start seeds indoors six to eight weeks earlier.

Nearby in Iowa

All 27 cities in Iowa