Last frost date in Decatur, IL

Average last frost
April 14

Expect the last frost in Decatur around April 14. Frost after May 1 happens in only one year out of ten. The first fall frost usually arrives about October 24, which leaves 192 frost-free days. An early freeze before October 11 happens one year in ten.

Safe after (10% risk)
May 1
Average first frost
Oct 24
Frost-free season
192 days
Hard freeze (28°F) ends
Apr 3
Next 7 nights in Decatur

No frost in the next 7 nights

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

  1. ThuOct 2245°
  2. FriOct 2344°
  3. SatOct 2446°
  4. SunOct 2549°
  5. MonOct 2649°
  6. TueOct 2745°
  7. WedOct 2846°
JanFebMarAprMayJunJulAugSepOctNovDecLast frost Apr 14First frost Oct 24192 frost-free daysBlue: chance of 32°F frost. Green: average frost-free season.JFMAMJJASOND192 frost-free days
Frost risk through the year at Decatur Water Plant, 2.1 miles from Decatur.

Planting calendar for Decatur

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
TomatoesApr 21–May 5
PumpkinsApr 28–May 12
SunflowersApr 14–May 5
CucumbersApr 28–May 5
CornApr 21–May 5
Sweet potatoesMay 5–May 19
WatermelonApr 28–May 12
Green beansApr 21–May 12
ZucchiniApr 21–May 5
OkraMay 5–May 19
PeppersApr 28–May 12
BasilApr 21–May 5
Butternut squashApr 21–May 5
CantaloupeApr 28–May 12
EggplantApr 28–May 12
Cool-season crops
JanFebMarAprMayJunJulAugSepOctNovDec
PotatoesMar 17–Mar 31
OnionsMar 3–Mar 24
CarrotsMar 24–Apr 28
LettuceMar 31–Apr 21
BroccoliMar 17–Mar 31
BeetsMar 17–Apr 28
PeasMar 3–Mar 17
CabbageMar 17–Mar 31
RadishesMar 10–Apr 21
Brussels sproutsMar 31–Apr 14
SpinachMar 3–Mar 24
CilantroMar 31–Apr 21
KaleMar 17–Mar 31
Collard greensMar 17–Mar 31
TurnipsMar 17–Mar 31
DillApr 14–Apr 28
CeleryApr 21–Apr 28
CauliflowerMar 31–Apr 14
LeeksMar 31–Apr 14
Swiss chardMar 31–Apr 28
ParsleyMar 31–Apr 21
Fall bulbs and garlic
JanFebMarAprMayJunJulAugSepOctNovDec
Tulip bulbsOct 10–Nov 14
GarlicOct 3–Nov 7
Daffodil bulbsSep 26–Nov 7
Perennials
JanFebMarAprMayJunJulAugSepOctNovDec
StrawberriesMar 17–Mar 31
AsparagusMar 17–Mar 31

Frost probabilities

ThresholdSpring, 90% chance laterSpring, 50%Spring, 10%Fall, 10% chance earlierFall, 50%Fall, 90%
Light frost, 32°FApr 1Apr 14May 1Oct 11Oct 24Nov 5
Hard freeze, 28°FMar 18Apr 3Apr 17Oct 20Nov 3Nov 19

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 Decatur Water Plant (USC00112193) sits 2.1 miles from the center of Decatur at 639 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 Decatur, IL?

The average last frost date in Decatur is April 14, based on NOAA 1991–2020 climate normals. There is a 10% chance of frost after May 1.

When is the first frost in Decatur?

The first frost in fall usually comes around October 24. One year in ten it arrives before October 11.

How long is the growing season in Decatur?

About 192 days between the average last and first frost.

When should I plant tomatoes in Decatur?

Plant tomato seedlings outside from April 21 to May 5. Start seeds indoors six to eight weeks earlier.

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