Last frost date in Iowa City, IA
Expect the last frost in Iowa City around April 21. Frost after May 6 happens in only one year out of ten. The first fall frost usually arrives about October 18, which leaves 180 frost-free days. An early freeze before October 4 happens one year in ten.
- Safe after (10% risk)
- May 6
- Average first frost
- Oct 18
- Frost-free season
- 180 days
- Hard freeze (28°F) ends
- Apr 9
No frost in the next 7 nights
Later than usual: the average first frost here is October 18.
National Weather Service forecast, updated Oct 22, 12:57 UTC
- ThuOct 2252°
- FriOct 2354°
- SatOct 2454°
- SunOct 2553°
- MonOct 2649°
- TueOct 2745°
- WedOct 2847°
Planting calendar for Iowa City
Windows count forward or back from the average frost dates above. Click a crop for dates across Iowa.
TomatoesApr 28–May 12
PumpkinsMay 5–May 19
SunflowersApr 21–May 12
CucumbersMay 5–May 12
CornApr 28–May 12
Sweet potatoesMay 12–May 26
WatermelonMay 5–May 19
Green beansApr 28–May 19
ZucchiniApr 28–May 12
OkraMay 12–May 26
PeppersMay 5–May 19
BasilApr 28–May 12
Butternut squashApr 28–May 12
CantaloupeMay 5–May 19
EggplantMay 5–May 19
PotatoesMar 24–Apr 7
OnionsMar 10–Mar 31
CarrotsMar 31–May 5
LettuceApr 7–Apr 28
BroccoliMar 24–Apr 7
BeetsMar 24–May 5
PeasMar 10–Mar 24
CabbageMar 24–Apr 7
RadishesMar 17–Apr 28
Brussels sproutsApr 7–Apr 21
SpinachMar 10–Mar 31
CilantroApr 7–Apr 28
KaleMar 24–Apr 7
Collard greensMar 24–Apr 7
TurnipsMar 24–Apr 7
DillApr 21–May 5
CeleryApr 28–May 5
CauliflowerApr 7–Apr 21
LeeksApr 7–Apr 21
Swiss chardApr 7–May 5
ParsleyApr 7–Apr 28
Tulip bulbsOct 4–Nov 8
GarlicSep 27–Nov 1
Daffodil bulbsSep 20–Nov 1
StrawberriesMar 24–Apr 7
AsparagusMar 24–Apr 7Frost probabilities
| Threshold | Spring, 90% chance later | Spring, 50% | Spring, 10% | Fall, 10% chance earlier | Fall, 50% | Fall, 90% |
|---|---|---|---|---|---|---|
| Light frost, 32°F | Apr 5 | Apr 21 | May 6 | Oct 4 | Oct 18 | Oct 31 |
| Hard freeze, 28°F | Mar 25 | Apr 9 | Apr 27 | Oct 15 | Oct 28 | Nov 9 |
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 Iowa City Municipal Airport (USW00014937) sits 1.7 miles from the center of Iowa City at 650 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 Iowa City, IA?
The average last frost date in Iowa City is April 21, based on NOAA 1991–2020 climate normals. There is a 10% chance of frost after May 6.
When is the first frost in Iowa City?
The first frost in fall usually comes around October 18. One year in ten it arrives before October 4.
How long is the growing season in Iowa City?
About 180 days between the average last and first frost.
When should I plant tomatoes in Iowa City?
Plant tomato seedlings outside from April 28 to May 12. Start seeds indoors six to eight weeks earlier.
Nearby in Iowa
- CoralvilleApr 21
- North LibertyApr 21
- Cedar RapidsApr 27
- MarionApr 28
- MuscatineApr 24
- DavenportApr 19
- BettendorfApr 16
- BurlingtonApr 15
- OttumwaApr 23
- ClintonApr 22
- WaterlooApr 27
- DubuqueApr 19