Frost Line Depth in McLean County, Illinois
- 4 verified codes nearby
- Checked Oct 2026
No official local value
No official frost line depth is published for McLean County.
Nearby official codes require 36–42 in (4 verified codes).
Source and how we checked
We searched this place’s own code and website and found no published frost line depth.
Climate: 133 nights a year at or below 32 °F (NOAA 1991–2020, Normal 4Ne, 6.7 mi).
Checked Oct 2026. Report a correction
Does McLean County have an official frost line depth?
No adopted frost line depth found for McLean County in its official documents (checked Oct 2026). The nearest official values, from codes we verified, are 36 to 42 in. Use the deepest of them until the building department confirms McLean County’s own number.
What frost line depth does McLean County use for footings under Table R301.2(1)? Is it 40 in, like Bloomington?
How deep do footings, decks and water lines need to be in McLean County?
Drawn with the deepest nearby official value (42 in). Confirm McLean County’s own depth before you dig.
House or garage footing in McLean 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 McLean County?
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
Average lows are at or below freezing from Nov to Mar. 133 nights a year reach 32 °F or colder; Jan is coldest, with an average low of 15.6 °F.
NOAA 1991–2020 climate normals, Normal 4ne station, 6.7 mi away, elevation 790 ft.
Monthly temperatures as a table
| °F | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Low | 15.6 | 18.9 | 27.8 | 37.9 | 49.8 | 59.9 | 63 | 60.8 | 53 | 41.8 | 30.7 | 21.4 |
| High | 33.4 | 38.2 | 49.8 | 62.8 | 74 | 83.3 | 86 | 84.4 | 78.8 | 65.6 | 50.2 | 38.3 |
McLean County has more freezing nights than 46 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 McLean County use?
4 official codes near McLean County are verified; each links to its document.
| Place | Verified frost line | Distance |
|---|---|---|
| Bloomington | 40 in | 7 mi away |
| Decatur | 36 in | 44 mi away |
| Peoria County | 42 in | 52 mi away |
| LaSalle County | 42 in | 59 mi away |
How likely is the soil in McLean County to heave?
USDA rates the sampled soil around McLean County as 48% moderate, 52% high for frost action (main soils: Ipava, Catlin, Ashkum).
USDA NRCS soil survey, 9 sample points within 2 mi. Higher frost action means more risk of heave; see frost heave.
McLean County at a glance
- Frost line depth
- No official local value
- Population (2023 est.)
- 170,441
- Mean annual temperature
- 51.1 °F
- ZIP codes (33)
- 60936 · 61701 · 61704 · 61705 · 61720 · 61722 · 61723 · 61724 · 61725 · 61726 · 61728 · 61729 · 61730 · 61731 · 61732 · 61736 · 61737 · 61738 · 61739 · 61744 · 61745 · 61748 · 61752 · 61753 · 61754 · 61761 · 61770 · 61772 · 61774 · 61776 · 61842 · 61843 · 61854