Last frost date in St. Charles, IL

Average last frost
April 25

Expect the last frost in St. Charles around April 25. Frost after May 12 happens in only one year out of ten. The first fall frost usually arrives about October 19, which leaves 174 frost-free days. An early freeze before October 5 happens one year in ten.

Safe after (10% risk)
May 12
Average first frost
Oct 19
Frost-free season
174 days
Hard freeze (28°F) ends
Apr 14
Next 7 nights in St. Charles

No frost in the next 7 nights

Later than usual: the average first frost here is October 19.

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

  1. ThuOct 2247°
  2. FriOct 2347°
  3. SatOct 2449°
  4. SunOct 2550°
  5. MonOct 2648°
  6. TueOct 2744°
  7. WedOct 2845°
JanFebMarAprMayJunJulAugSepOctNovDecLast frost Apr 25First frost Oct 19174 frost-free daysBlue: chance of 32°F frost. Green: average frost-free season.JFMAMJJASOND174 frost-free days
Frost risk through the year at West Chicago Dupage Airport, 3.3 miles from St. Charles.

Planting calendar for St. Charles

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

Start indoorsPlant outSow outdoorsFall plantingAverage last and first frost
Warm-season crops
JanFebMarAprMayJunJulAugSepOctNovDec
TomatoesMay 2–May 16
PumpkinsMay 9–May 23
SunflowersApr 25–May 16
CucumbersMay 9–May 16
CornMay 2–May 16
Sweet potatoesMay 16–May 30
WatermelonMay 9–May 23
Green beansMay 2–May 23
ZucchiniMay 2–May 16
OkraMay 16–May 30
PeppersMay 9–May 23
BasilMay 2–May 16
Butternut squashMay 2–May 16
CantaloupeMay 9–May 23
EggplantMay 9–May 23
Cool-season crops
JanFebMarAprMayJunJulAugSepOctNovDec
PotatoesMar 28–Apr 11
OnionsMar 14–Apr 4
CarrotsApr 4–May 9
LettuceApr 11–May 2
BroccoliMar 28–Apr 11
BeetsMar 28–May 9
PeasMar 14–Mar 28
CabbageMar 28–Apr 11
RadishesMar 21–May 2
Brussels sproutsApr 11–Apr 25
SpinachMar 14–Apr 4
CilantroApr 11–May 2
KaleMar 28–Apr 11
Collard greensMar 28–Apr 11
TurnipsMar 28–Apr 11
DillApr 25–May 9
CeleryMay 2–May 9
CauliflowerApr 11–Apr 25
LeeksApr 11–Apr 25
Swiss chardApr 11–May 9
ParsleyApr 11–May 2
Fall bulbs and garlic
JanFebMarAprMayJunJulAugSepOctNovDec
Tulip bulbsOct 5–Nov 9
GarlicSep 28–Nov 2
Daffodil bulbsSep 21–Nov 2
Perennials
JanFebMarAprMayJunJulAugSepOctNovDec
StrawberriesMar 28–Apr 11
AsparagusMar 28–Apr 11

Frost probabilities

ThresholdSpring, 90% chance laterSpring, 50%Spring, 10%Fall, 10% chance earlierFall, 50%Fall, 90%
Light frost, 32°FApr 11Apr 25May 12Oct 5Oct 19Oct 30
Hard freeze, 28°FMar 31Apr 14Apr 29Oct 16Oct 29Nov 12

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 West Chicago Dupage Airport (USW00094892) sits 3.3 miles from the center of St. Charles at 754 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 St. Charles, IL?

The average last frost date in St. Charles is April 25, based on NOAA 1991–2020 climate normals. There is a 10% chance of frost after May 12.

When is the first frost in St. Charles?

The first frost in fall usually comes around October 19. One year in ten it arrives before October 5.

How long is the growing season in St. Charles?

About 174 days between the average last and first frost.

When should I plant tomatoes in St. Charles?

Plant tomato seedlings outside from May 2 to May 16. Start seeds indoors six to eight weeks earlier.

Nearby in Illinois

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