Last frost date in Sioux City, IA

Average last frost
April 29

In Sioux City, the last spring frost comes around April 29 in an average year. Wait until May 11 if you want 90% odds of no more frost. The first fall frost usually arrives about October 7, which leaves 161 frost-free days. An early freeze before September 24 happens one year in ten.

Safe after (10% risk)
May 11
Average first frost
Oct 7
Frost-free season
161 days
Hard freeze (28°F) ends
Apr 19
Next 7 nights in Sioux City

No frost in the next 7 nights

Later than usual: the average first frost here is October 7.

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

  1. ThuOct 2258°
  2. FriOct 2361°
  3. SatOct 2449°
  4. SunOct 2545°
  5. MonOct 2641°
  6. TueOct 2740°
  7. WedOct 2842°
JanFebMarAprMayJunJulAugSepOctNovDecLast frost Apr 29First frost Oct 7161 frost-free daysBlue: chance of 32°F frost. Green: average frost-free season.JFMAMJJASOND161 frost-free days
Frost risk through the year at Sioux City Ang, 6.9 miles from Sioux City.

Planting calendar for Sioux City

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
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 23–Oct 28
GarlicSep 16–Oct 21
Daffodil bulbsSep 9–Oct 21
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 11Sep 24Oct 7Oct 21
Hard freeze, 28°FApr 5Apr 19May 2Oct 2Oct 18Oct 30

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 Sioux City Ang (USC00137702) sits 6.9 miles from the center of Sioux City at 1,100 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 Sioux City, IA?

The average last frost date in Sioux City is April 29, based on NOAA 1991–2020 climate normals. There is a 10% chance of frost after May 11.

When is the first frost in Sioux City?

The first frost in fall usually comes around October 7. One year in ten it arrives before September 24.

How long is the growing season in Sioux City?

About 161 days between the average last and first frost.

When should I plant tomatoes in Sioux City?

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

Nearby in Iowa

All 27 cities in Iowa