Last frost date in Mount Prospect, IL

Average last frost
April 19

Expect the last frost in Mount Prospect around April 19. Frost after May 3 happens in only one year out of ten. The first fall frost usually arrives about October 26, which leaves 190 frost-free days. An early freeze before October 13 happens one year in ten.

Safe after (10% risk)
May 3
Average first frost
Oct 26
Frost-free season
190 days
Hard freeze (28°F) ends
Apr 5
Next 7 nights in Mount Prospect

No frost in the next 7 nights

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

  1. ThuOct 2249°
  2. FriOct 2350°
  3. SatOct 2452°
  4. SunOct 2553°
  5. MonOct 2650°
  6. TueOct 2747°
  7. WedOct 2848°
JanFebMarAprMayJunJulAugSepOctNovDecLast frost Apr 19First frost Oct 26190 frost-free daysBlue: chance of 32°F frost. Green: average frost-free season.JFMAMJJASOND190 frost-free days
Frost risk through the year at Chicago Palwaukee Airport, 4.3 miles from Mount Prospect.

Planting calendar for Mount Prospect

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 26–May 10
PumpkinsMay 3–May 17
SunflowersApr 19–May 10
CucumbersMay 3–May 10
CornApr 26–May 10
Sweet potatoesMay 10–May 24
WatermelonMay 3–May 17
Green beansApr 26–May 17
ZucchiniApr 26–May 10
OkraMay 10–May 24
PeppersMay 3–May 17
BasilApr 26–May 10
Butternut squashApr 26–May 10
CantaloupeMay 3–May 17
EggplantMay 3–May 17
Cool-season crops
JanFebMarAprMayJunJulAugSepOctNovDec
PotatoesMar 22–Apr 5
OnionsMar 8–Mar 29
CarrotsMar 29–May 3
LettuceApr 5–Apr 26
BroccoliMar 22–Apr 5
BeetsMar 22–May 3
PeasMar 8–Mar 22
CabbageMar 22–Apr 5
RadishesMar 15–Apr 26
Brussels sproutsApr 5–Apr 19
SpinachMar 8–Mar 29
CilantroApr 5–Apr 26
KaleMar 22–Apr 5
Collard greensMar 22–Apr 5
TurnipsMar 22–Apr 5
DillApr 19–May 3
CeleryApr 26–May 3
CauliflowerApr 5–Apr 19
LeeksApr 5–Apr 19
Swiss chardApr 5–May 3
ParsleyApr 5–Apr 26
Fall bulbs and garlic
JanFebMarAprMayJunJulAugSepOctNovDec
Tulip bulbsOct 12–Nov 16
GarlicOct 5–Nov 9
Daffodil bulbsSep 28–Nov 9
Perennials
JanFebMarAprMayJunJulAugSepOctNovDec
StrawberriesMar 22–Apr 5
AsparagusMar 22–Apr 5

Frost probabilities

ThresholdSpring, 90% chance laterSpring, 50%Spring, 10%Fall, 10% chance earlierFall, 50%Fall, 90%
Light frost, 32°FApr 4Apr 19May 3Oct 13Oct 26Nov 9
Hard freeze, 28°FMar 22Apr 5Apr 20Oct 26Nov 7Nov 21

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 Chicago Palwaukee Airport (USW00004838) sits 4.3 miles from the center of Mount Prospect at 636 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 Mount Prospect, IL?

The average last frost date in Mount Prospect is April 19, based on NOAA 1991–2020 climate normals. There is a 10% chance of frost after May 3.

When is the first frost in Mount Prospect?

The first frost in fall usually comes around October 26. One year in ten it arrives before October 13.

How long is the growing season in Mount Prospect?

About 190 days between the average last and first frost.

When should I plant tomatoes in Mount Prospect?

Plant tomato seedlings outside from April 26 to May 10. Start seeds indoors six to eight weeks earlier.

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