Chicago, Illinois, United States

Frost dates for Chicago

The full distribution rather than a single date. Every figure below is a percentile of 30 years of daily minimum temperatures at this location, expressed as the date it fell on.

Median last spring frost

4 April

Half of years are later than this. Not a planting date.

Median first autumn frost

17 November

The far end of the outdoor season.

Frost-free season

227 days

Between those two dates in a median year.

Last and first frost by severity

Read a row as: in this fraction of years, the last frost of spring had already happened by this date. The 90% column is the cautious planting date; the 10% column is the gamble.

Light frost — nights at or below 0°C (32°F). Air temperature reaches freezing. Kills basil, beans and unhardened tomatoes; hardy crops shrug it off.
Frost 1 year in 10 Median 9 years in 10 Earliest Latest
Last of spring 23 Mar 4 Apr 17 Apr 11 Mar 20 Apr
First of autumn 3 Nov 17 Nov 2 Dec 1 Nov 20 Dec
Frost-free days 254 227 200 every year on record saw this
Moderate frost — nights at or below -2.2°C (28°F). Damages half-hardy plants and most blossom. This is the threshold that decides a fruit crop.
Frost 1 year in 10 Median 9 years in 10 Earliest Latest
Last of spring 1 Mar 24 Mar 9 Apr 21 Feb 16 Apr
First of autumn 13 Nov 27 Nov 17 Dec 7 Nov 23 Dec
Frost-free days 291 248 218 every year on record saw this
Hard frost — nights at or below -4.4°C (24.1°F). Ground freezes and even hardy crops check their growth. Effectively the end of the outdoor year.
Frost 1 year in 10 Median 9 years in 10 Earliest Latest
Last of spring 25 Feb 13 Mar 28 Mar 20 Feb 7 Apr
First of autumn 19 Nov 6 Dec 24 Dec 11 Nov 31 Dec
Frost-free days 303 268 236 every year on record saw this

Dates in the southern hemisphere are computed on a growing year that starts in July, which is why "last of spring" falls where it should rather than in the middle of the calendar.

Chance of frost, week by week

Jan Mar Apr Jul Sep Oct Dec
Chance of at least one air frost during each week of the year, measured across the full record. The flat stretch in the middle is your frost-free season.

Temperature through the year

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Mean monthly temperature across the record. Months shown in blue average at least one air frost.

Monthly means and average number of frost nights.
Month Mean low Mean high Frost nights
January -4.9°C -0.2°C 25.7
February -4.5°C 0.8°C 23.6
March -0.5°C 5.1°C 16.9
April 3.8°C 10°C 2.7
May 8.8°C 15.2°C 0
June 15.1°C 21.1°C 0
July 19.6°C 24.9°C 0
August 20°C 25.1°C 0
September 16.4°C 22°C 0
October 9.9°C 15.6°C 0
November 3.4°C 8.5°C 5.5
December -1.8°C 2.7°C 18.4

Turn these dates into a planting calendar →

Nearby

Compare with places close by

Cicero Zone 7a 9 km Last frost 4 Apr First 17 Nov Oak Park Zone 7a 12 km Last frost 4 Apr First 17 Nov Berwyn Zone 7a 12 km Last frost 4 Apr First 17 Nov Oak Lawn Zone 6a 18 km Last frost 22 Apr First 31 Oct Evanston Zone 7a 22 km Last frost 4 Apr First 17 Nov Skokie Zone 7a 22 km Last frost 4 Apr First 17 Nov Des Plaines Zone 5b 28 km Last frost 26 Apr First 22 Oct Orland Park Zone 5b 30 km Last frost 25 Apr First 22 Oct

Seasonal context

Rainfall and the growing season in Chicago

May has the highest average precipitation (119 mm); January has the lowest (47 mm). Compare this pattern with the planting windows and your water supply.

Jan 47 mm
Feb 53 mm
Mar 62 mm
Apr 93 mm
May 119 mm
Jun 102 mm
Jul 96 mm
Aug 105 mm
Sep 86 mm
Oct 98 mm
Nov 61 mm
Dec 59 mm

During wetter months, check that beds and containers drain after heavy rain. During drier months, plan how you will keep seeds and new transplants watered. Monthly averages can hide long dry spells and intense storms; they do not show soil moisture, humidity or this week's weather.

Source: NASA POWER, corrected MERRA-2 precipitation, 2001–2020. Values are approximate monthly totals, including the water equivalent of snow, from the nearest 0.5° × 0.625° grid cell. This reference period differs from the temperature record. Rainfall provides context and does not change the calculated planting dates. Method and limitations.

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