Frostline.info

Frost line depth in Cook County, Illinois

Frost reaches about 37 inches in typical soil across Cook County, from 34″ in the mildest ZIP code to 40″ in the coldest. Codes in this climate commonly set footing depth at 30 to 48 inches.

Deep frost
Estimated frost depth
37″
typical silt/loam soil
Typical code footing depth
30–48″
rule of thumb for this climate
Design freezing index
1,421
°F-days, 100-year winter
ZIP codes covered
165
#35 of 102 counties in IL (1 = deepest)
37″ 0″12″24″36″48″60″ ground frozen
Est. frost (typical soil) Typical code footing depth Clay–sand range

Frost depth by soil type

Soil typeEst. frost depth
Sand / gravel (drains well)47″
Silt / loam (typical yard soil)37″
Clay (holds water)32″

County average. Methodology.

Verify before you dig. These are climate-based estimates. The legally required frost depth is the figure your building department publishes in its IRC Table R301.2 (climatic and geographic design criteria). Call the Cook County building or permitting office in Illinois and call 811 before digging.

Frost depth by ZIP code in Cook County

ZIPCityEst. frostCode range
60004Arlington Heights39″36–48″
60005Arlington Heights39″30–48″
60007Elk Grove Village39″30–48″
60008Rolling Meadows39″36–48″
60016Des Plaines39″30–48″
60018Des Plaines37″30–48″
60022Glencoe38″30–48″
60025Glenview39″30–48″
60026Glenview38″30–48″
60043Kenilworth38″30–48″
60053Morton Grove37″30–48″
60056Mount Prospect39″30–48″
60062Northbrook39″36–48″
60067Palatine40″36–48″
60068Park Ridge37″30–48″
60070Prospect Heights39″36–48″
60074Palatine40″36–54″
60076Skokie36″30–48″
60077Skokie37″30–48″
60090Wheeling39″36–48″
60091Wilmette37″30–48″
60093Winnetka38″30–48″
60104Bellwood37″30–48″
60107Streamwood39″36–48″
60120Elgin40″36–48″
60130Forest Park37″30–48″
60131Franklin Park37″30–48″
60133Hanover Park39″30–48″
60153Maywood37″30–48″
60154Westchester37″30–48″
60155Broadview37″30–48″
60160Melrose Park37″30–48″
60162Hillside37″30–48″
60163Berkeley37″30–48″
60164Melrose Park37″30–48″
60165Stone Park37″30–48″
60169Hoffman Estates39″36–48″
60171River Grove37″30–48″
60173Schaumburg39″30–48″
60176Schiller Park37″30–48″
60192Hoffman Estates39″36–48″
60193Schaumburg39″30–48″
60194Schaumburg39″36–48″
60195Schaumburg39″36–48″
60201Evanston37″30–48″
60202Evanston37″30–48″
60203Evanston37″30–48″
60301Oak Park37″30–48″
60302Oak Park37″30–48″
60304Oak Park37″30–48″
60305River Forest37″30–48″
60402Berwyn37″30–48″
60406Blue Island37″30–48″
60409Calumet City37″30–48″
60411Chicago Heights39″30–48″
60415Chicago Ridge37″30–48″
60418Crestwood37″30–48″
60419Dolton37″30–48″
60422Flossmoor39″36–48″
60425Glenwood39″30–48″
60426Harvey38″30–48″
60428Markham38″30–48″
60429Hazel Crest39″30–48″
60430Homewood39″30–48″
60438Lansing38″30–48″
60439Lemont38″30–48″
60443Matteson39″36–48″
60445Midlothian37″30–48″
60452Oak Forest38″30–48″
60453Oak Lawn37″30–48″
60455Bridgeview37″30–48″
60456Hometown37″30–48″
60457Hickory Hills37″30–48″
60458Justice37″30–48″
60459Burbank37″30–48″
60461Olympia Fields39″36–48″
60462Orland Park37″30–48″
60463Palos Heights37″30–48″
60464Palos Park38″30–48″
60465Palos Hills37″30–48″
60466Park Forest39″36–48″
60467Orland Park38″30–48″
60469Posen37″30–48″
60471Richton Park39″36–48″
60472Robbins37″30–48″
60473South Holland38″30–48″
60476Thornton38″30–48″
60477Tinley Park38″30–48″
60478Country Club Hills39″30–48″
60480Willow Springs37″30–48″
60482Worth37″30–48″
60487Tinley Park38″30–48″
60501Summit Argo37″30–48″
60513Brookfield37″30–48″
60525La Grange37″30–48″
60526La Grange Park37″30–48″
60534Lyons37″30–48″
60546Riverside37″30–48″
60558Western Springs37″30–48″
60601Chicago35″30–48″
60602Chicago35″30–48″
60603Chicago35″30–48″
60604Chicago35″30–48″
60605Chicago35″30–48″
60606Chicago36″30–48″
60607Chicago36″30–48″
60608Chicago36″30–48″
60609Chicago35″30–42″
60610Chicago36″30–48″
60611Chicago36″30–48″
60612Chicago36″30–48″
60613Chicago36″30–48″
60614Chicago36″30–48″
60615Chicago34″30–42″
60616Chicago35″30–42″
60617Chicago35″30–42″
60618Chicago36″30–48″
60619Chicago34″30–42″
60620Chicago35″30–48″
60621Chicago35″30–42″
60622Chicago36″30–48″
60623Chicago36″30–48″
60624Chicago36″30–48″
60625Chicago36″30–48″
60626Chicago36″30–48″
60628Chicago36″30–48″
60629Chicago37″30–48″
60630Chicago37″30–48″
60631Chicago37″30–48″
60632Chicago37″30–48″
60633Chicago36″30–48″
60634Chicago37″30–48″
60636Chicago35″30–48″
60637Chicago34″30–42″
60638Chicago37″30–48″
60639Chicago36″30–48″
60640Chicago36″30–48″
60641Chicago36″30–48″
60642Chicago36″30–48″
60643Chicago36″30–48″
60644Chicago37″30–48″
60645Chicago36″30–48″
60646Chicago37″30–48″
60647Chicago36″30–48″
60649Chicago34″30–42″
60651Chicago36″30–48″
60652Chicago37″30–48″
60653Chicago34″30–42″
60654Chicago36″30–48″
60655Chicago36″30–48″
60656Chicago37″30–48″
60657Chicago36″30–48″
60659Chicago36″30–48″
60660Chicago36″30–48″
60661Chicago36″30–48″
60699Chicago36″30–48″
60701Chicago36″30–48″
60706Harwood Heights37″30–48″
60707Elmwood Park37″30–48″
60712Lincolnwood36″30–48″
60714Niles37″30–48″
60803Alsip37″30–48″
60804Cicero37″30–48″
60805Evergreen Park36″30–48″
60827Riverdale37″30–48″

What this means for your project in Cook County

Deck footings & piers

Footings must bear below the frost line and at least 12″ below undisturbed ground. For planning in this area, budget for holes around 48″ deep until your permit office confirms the exact figure.

Fence posts

Set posts at least one-third of their above-ground height. Where frost heave is a problem, carry concrete footings below the frost line (about 37″ here in typical soil) and bell or taper the bottom.

Water & irrigation lines

Bury supply lines below the frost depth. Your water utility or plumbing code sets the minimum cover; in a climate this cold, 4 feet or more is common for service lines.

Slabs & frost-protected foundations

Frost-protected shallow foundations (IRC R403.3) use the 100-year air freezing index — 1,421 °F-days here — to size perimeter insulation, letting footings sit shallower than the frost line.

Weather stations used

NOAA weather stationDistance100-yr AFI
Chicago Midway Airport, IL5 mi1,433
Chicago University, IL10 mi1,197
Wheaton 3 Se, IL15 mi1,543
Park Forest, IL24 mi1,583

Nearby counties

Common questions

What is the frost line depth in Cook County?

About 37 inches in typical soil, based on NOAA's 100-year air freezing index. Across the county's ZIP codes the estimate runs from 34 to 40 inches.

How deep should footings be in Cook County, Illinois?

Codes in climates like this commonly require 30 to 48 inches. The Cook County building department publishes the required frost depth in its adopted code (IRC Table R301.2).

Does frost depth vary within Cook County?

Yes. Estimates differ by 6 inches between the coldest and mildest ZIP codes, mostly from latitude and elevation. Check your own ZIP below.