Frost Line Depth in Cook County, Illinois
- 5 verified codes nearby
- Checked Oct 2026
No official local value
No official frost line depth is published for Cook County.
Nearby official codes require 42 in (5 verified codes).
Source and how we checked
We searched this place’s own code and website and found no published frost line depth.
Climate: 97 nights a year at or below 32 °F (NOAA 1991–2020, Chicago Northerly Is, 3.2 mi).
Checked Oct 2026. Report a correction
Does Cook County have an official frost line depth?
No adopted frost line depth found for Cook County in its official documents (checked Oct 2026). The nearest official values, from codes we verified, are 42 in. Use the deepest of them until the building department confirms Cook County’s own number.
What frost line depth does Cook County use for footings under Table R301.2(1)? Is it 42 in, like Glenview?
How deep do footings, decks and water lines need to be in Cook County?
Drawn with the deepest nearby official value (42 in). Confirm Cook County’s own depth before you dig.
House or garage footing in Cook County: dig at least 42 in (107 cm). Below the frost line and at least 12 in deep (IRC R403.1.4).
| Project | Depth | Rule |
|---|---|---|
| House or garage footing | 42 in | Below the frost line and at least 12 in deep (IRC R403.1.4) |
| Deck footing (attached) | 42 in | Below the frost line and at least 12 in deep (IRC R507.3) |
| Water service line | 48 in | 6 in below the frost line and at least 12 in deep (IRC P2603.5) |
| Fence post bottom | 42 in | No code rule; common practice is below the frost line |
Work out posts, concrete and footing sizes with the fence post depth calculator or the deck footing calculator.
How cold does it get in Cook County?
- J
- F
- M
- A
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- J
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- D
Average lows are at or below freezing from Dec to Mar. 97 nights a year reach 32 °F or colder; Jan is coldest, with an average low of 20.1 °F.
NOAA 1991–2020 climate normals, Chicago Northerly Is station, 3.2 mi away, elevation 583 ft.
Monthly temperatures as a table
| °F | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Low | 20.1 | 23.1 | 30.9 | 40.4 | 50.1 | 60 | 67.3 | 67.4 | 60.2 | 47.7 | 36.4 | 25.2 |
| High | 31.9 | 35.7 | 44.9 | 55.2 | 65.7 | 75.8 | 81 | 80 | 73.2 | 60.9 | 48.5 | 36.6 |
Cook County has fewer freezing nights than 66 of the 71 other Illinois places we track. The Illinois median is 127. Coldest: Hoffman Estates; mildest: Madison County.
What frost line depth do towns near Cook County use?
5 official codes near Cook County are verified; each links to its document.
| Place | Verified frost line | Distance |
|---|---|---|
| Glenview | 42 in | 16 mi away |
| Lombard | 42 in | 19 mi away |
| Wheaton | 42 in | 24 mi away |
| Palatine | 42 in | 26 mi away |
| Bolingbrook | 42 in | 27 mi away |
How likely is the soil in Cook County to heave?
USDA rates the sampled soil around Cook County as 97% moderate, 3% high for frost action (main soils: Orthents, Orthents, clayey, Ashkum).
USDA NRCS soil survey, 9 sample points within 2 mi. Higher frost action means more risk of heave; see frost heave.
Cook County at a glance
- Frost line depth
- No official local value
- Population (2023 est.)
- 5,087,072
- Mean annual temperature
- 50.8 °F
- ZIP codes (178)
- 60004 · 60005 · 60007 · 60008 · 60010 · 60015 · 60016 · 60018 · 60022 · 60025 · 60026 · 60029 · 60043 · 60053 · 60056 · 60062 · 60067 · 60068 · 60070 · 60074 · 60076 · 60077 · 60089 · 60090 · 60091 · 60093 · 60103 · 60104 · 60107 · 60120 · 60126 · 60130 · 60131 · 60133 · 60141 · 60153 · 60154 · 60155 · 60160 · 60162 · 60163 · 60164 · 60165 · 60169 · 60171 · 60172 · 60173 · 60176 · 60192 · 60193 · 60194 · 60195 · 60201 · 60202 · 60203 · 60208 · 60301 · 60302 · 60304 · 60305 · 60402 · 60406 · 60409 · 60411 · 60415 · 60418 · 60419 · 60422 · 60423 · 60425 · 60426 · 60428 · 60429 · 60430 · 60438 · 60439 · 60443 · 60445 · 60449 · 60452 · 60453 · 60455 · 60456 · 60457 · 60458 · 60459 · 60461 · 60462 · 60463 · 60464 · 60465 · 60466 · 60467 · 60469 · 60471 · 60472 · 60473 · 60475 · 60476 · 60477 · 60478 · 60480 · 60482 · 60487 · 60501 · 60513 · 60521 · 60523 · 60525 · 60526 · 60527 · 60534 · 60546 · 60558 · 60601 · 60602 · 60603 · 60604 · 60605 · 60606 · 60607 · 60608 · 60609 · 60610 · 60611 · 60612 · 60613 · 60614 · 60615 · 60616 · 60617 · 60618 · 60619 · 60620 · 60621 · 60622 · 60623 · 60624 · 60625 · 60626 · 60628 · 60629 · 60630 · 60631 · 60632 · 60633 · 60634 · 60636 · 60637 · 60638 · 60639 · 60640 · 60641 · 60642 · 60643 · 60644 · 60645 · 60646 · 60647 · 60649 · 60651 · 60652 · 60653 · 60654 · 60655 · 60656 · 60657 · 60659 · 60660 · 60661 · 60706 · 60707 · 60712 · 60714 · 60803 · 60804 · 60805 · 60827