Last frost date in O'Fallon, MO

Average last frost
April 10

The average last frost in O'Fallon is April 10. By April 26 the chance of another 32°F night drops to 1 in 10. The first fall frost usually arrives about October 26, which leaves 199 frost-free days. An early freeze before October 12 happens one year in ten.

Safe after (10% risk)
Apr 26
Average first frost
Oct 26
Frost-free season
199 days
Hard freeze (28°F) ends
Mar 31
Next 7 nights in O'Fallon

No frost in the next 7 nights

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

  1. ThuOct 2248°
  2. FriOct 2347°
  3. SatOct 2449°
  4. SunOct 2550°
  5. MonOct 2649°
  6. TueOct 2746°
  7. WedOct 2848°
JanFebMarAprMayJunJulAugSepOctNovDecLast frost Apr 10First frost Oct 26199 frost-free daysBlue: chance of 32°F frost. Green: average frost-free season.JFMAMJJASOND199 frost-free days
Frost risk through the year at Weldon Spring NWS, 5.9 miles from O'Fallon.

Planting calendar for O'Fallon

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

Start indoorsPlant outSow outdoorsFall plantingAverage last and first frost
Warm-season crops
JanFebMarAprMayJunJulAugSepOctNovDec
TomatoesApr 17–May 1
PumpkinsApr 24–May 8
SunflowersApr 10–May 1
CucumbersApr 24–May 1
CornApr 17–May 1
Sweet potatoesMay 1–May 15
WatermelonApr 24–May 8
Green beansApr 17–May 8
ZucchiniApr 17–May 1
OkraMay 1–May 15
PeppersApr 24–May 8
BasilApr 17–May 1
Butternut squashApr 17–May 1
CantaloupeApr 24–May 8
EggplantApr 24–May 8
Cool-season crops
JanFebMarAprMayJunJulAugSepOctNovDec
PotatoesMar 13–Mar 27
OnionsFeb 27–Mar 20
CarrotsMar 20–Apr 24
LettuceMar 27–Apr 17
BroccoliMar 13–Mar 27
BeetsMar 13–Apr 24
PeasFeb 27–Mar 13
CabbageMar 13–Mar 27
RadishesMar 6–Apr 17
Brussels sproutsMar 27–Apr 10
SpinachFeb 27–Mar 20
CilantroMar 27–Apr 17
KaleMar 13–Mar 27
Collard greensMar 13–Mar 27
TurnipsMar 13–Mar 27
DillApr 10–Apr 24
CeleryApr 17–Apr 24
CauliflowerMar 27–Apr 10
LeeksMar 27–Apr 10
Swiss chardMar 27–Apr 24
ParsleyMar 27–Apr 17
Fall bulbs and garlic
JanFebMarAprMayJunJulAugSepOctNovDec
Tulip bulbsOct 12–Nov 16
GarlicOct 5–Nov 9
Daffodil bulbsSep 28–Nov 9
Perennials
JanFebMarAprMayJunJulAugSepOctNovDec
StrawberriesMar 13–Mar 27
AsparagusMar 13–Mar 27

Frost probabilities

ThresholdSpring, 90% chance laterSpring, 50%Spring, 10%Fall, 10% chance earlierFall, 50%Fall, 90%
Light frost, 32°FMar 26Apr 10Apr 26Oct 12Oct 26Nov 8
Hard freeze, 28°FMar 12Mar 31Apr 15Oct 22Nov 5Nov 22

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 Weldon Spring NWS (USC00238805) sits 5.9 miles from the center of O'Fallon at 610 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 O'Fallon, MO?

The average last frost date in O'Fallon is April 10, based on NOAA 1991–2020 climate normals. There is a 10% chance of frost after April 26.

When is the first frost in O'Fallon?

The first frost in fall usually comes around October 26. One year in ten it arrives before October 12.

How long is the growing season in O'Fallon?

About 199 days between the average last and first frost.

When should I plant tomatoes in O'Fallon?

Plant tomato seedlings outside from April 17 to May 1. Start seeds indoors six to eight weeks earlier.

Nearby in Missouri

All 41 cities in Missouri