Illinois Climate Data

We offer an Illinois Manual J for $79 in 4-6 hours.  We can also offer Illinois Manual S $79 and Illinois Manual D $99.

Below is a collection of Illinois Climate Data and outdoor design conditions. We included an Illinois state average of each category at the bottom of the Manual J climate data table. We created this to allow an easy to use free resource for Manual J professionals to use on jobsites, in the field, and while calculating Manual J heat loss and heat gain reports. If you have a custom set of data from Illinois we would consider adding to the Illinois Climate Data table simply email it to

We can also create a Manual J using climate data from the tables below. Email pdf plans, jobsite address, and square footage to and we will get your Illinois Manual J taken care of.

Free Manual J

IllinoisElevation in FeetLatitude North DegreesHeating 99% Outdoor Dry BulbCooling Outdoor Air 1% Dry BulbCooling Outdoor Air Coincident Wet BulbCooling Design Grains 55% Relative Humidity IndoorsCooling Design Grains 45% Relative Humidity IndoorsCooling Design Grains 45% Relative Humidity IndoorsDaily RatingHeating Design Days 65 degrees/Colling Design Days 50 degrees Ratio
Aurora Municipal airport7054218874303744M2.22
Belleville, Scott Air Force Base45338109377445158M1.13
Bloomington (Peoria DD)87540–29074313845M1.8
Cahokia, airport41339149176435056M1.06
Champaign, Urbana7544029274283441M1.77
Chicago, Meigs Field5934138973263340M1.72
Chicago Midway airport6174249073273441M1.77
Chicago Ohare international airport6734228973293642M2.08
Chicago CO6474129174293643L1.72
Glenview Naval Auxilary Air Station6534229073263239M2
Greenville (Vandalia DD)5413949275334047M1.49
LaSalle, Peru65441–29175354249M2.1
Lawrenceville-Vincennes international airport43039129176384552M1.16
Macomb (Galesburg DD)7054009276404754M1.96
Marseilles Island7384108974333946M2.04
Matoon Charleston airport7223999076424955M1.38
Moline Quad City international airport5944109175364350M1.83
Mount Vernon Automated Weather Observation System47938119176424855M1.25
Peoria, Greater Peoria airport6634129075394552M1.68
Baldwin Field7684039075384552M1.54
Rantoul, Chanute Air Force Base7374019174293643M1.78
Rockford, Greater Rockford airport74542-28974323845M2.27
Scott Air Force Base, Bellevill44339109377424955M1.11
Southern Illinois airport42038169177475360M1.01
Springfield Capital airport6144059176404653M1.48
Sterling Rockfalls6464208874323845M2.22
University of Illinois7744049075404653M1.63
West Chicago, Du Page airport7584218874334046M2.25
Illinois State Average64940.42105263164.193548387190.315789473774.736842105334.815789473741.421052631648.2105263158M1.8065789474
Illinois Climate Data
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Illinois Climate Data
Illinois Climate Data
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