Champaign Pavement Data: The Freeze Calendar, the Salt, the Soil and the Streets

Last reviewed 2026-07-25. Journalists, researchers, and community groups are welcome to cite any figure on this page with attribution and a link.

Most local service websites recycle national averages and call them local. This page does the opposite. Everything below comes from a specific published source about Champaign or Champaign County: the Illinois State Climatologist's normals for the Willard Airport and Champaign-Urbana records, the City of Champaign's own description of its winter operations, the USDA official series descriptions for the two soils whose reference locations sit in this county, a published analysis of the city's pavement condition data, and Census QuickFacts for Champaign city.

The point of assembling it in one place is that the argument for pavement maintenance in Champaign is not a general one. It rests on a specific and unusual combination: a very high count of shallow freezes, a modest snow total that is nonetheless treated with three different chloride products, a subgrade that is saturated for a third of the year, and a housing market where most occupied units are rented and park on shared lots. The guide on prairie clay and freeze-thaw explains the mechanism; this page is the evidence.

The Champaign freeze calendar

Temperature normals and freeze-day counts below are the Champaign Willard Airport station figures from the Illinois State Climatologist's 1981-2010 normals; the snowfall column comes from the same office's averages and records page for Champaign-Urbana. The single most useful number is the annual freeze count of 123.5 days at or below 32 degrees, which is more than a third of the year.

Read the January row carefully, because it is the whole argument in one line. The normal high is 33.5 degrees, above freezing. The normal low is 17.2 degrees, well below. The average January day in Champaign crosses the freezing line and crosses back. That is a freeze-thaw cycle occurring on a typical day in the coldest month, and it happens on roughly 27.7 days that month. The nearby Champaign 9 SW station records an even higher annual count at 126.6 days, so the Willard figure is if anything the conservative one.

Note also the shoulder months. October already carries 4.7 freeze days and April still carries 6.4. That matters for scheduling, because sealer needs a cure window that is not interrupted by an overnight freeze. The average last spring frost for Champaign-Urbana falls near April 15 and the average first fall frost near October 17, which brackets the working season neatly.

How cold it actually gets, and how rarely

The extremes are worth knowing because they set the range asphalt has to survive, but they are not what breaks pavement. Champaign-Urbana temperature and precipitation records run back to 1888, with snowfall records from 1903. In that entire record the highest reading is 109 degrees on July 14, 1954, and the lowest is 25 below zero, reached on four separate occasions including January 19, 1994 and January 5, 1999. That is a 134-degree spread over the life of the record.

Against that, the Willard normals record only about 6.1 days a year with a low at or below zero, and only 15.9 days a year with a high at or above 90. Champaign is a market of moderate but relentless cycling, not of extremes. Sixteen hot days and six severely cold ones against 123.5 freeze days tells you where the damage comes from.

The snow record has some genuinely large single events in it: 15 inches from the storm of January 1-2, 1999, a maximum ground depth of 19 inches on February 8-10, 1982, and a maximum seasonal total of 67.2 inches in the winter of 1977-78. A 23.2 inch average conceals a lot of variance, and a heavy winter means considerably more plowing, more chloride and more meltwater cycling than an average one.

What the city puts on the street, and what ends up on your pavement

The City of Champaign's published description of its snow and ice operations gives the specifics. The city runs 14 snow plow trucks, divides primary snow routes into seven separate routes varying between 19 and 25 miles in length, and treats those primary routes as roughly 50 percent of the total street system. Primary routes are targeted for completion within 12 hours of the end of a storm, secondary routes within 24 hours after that, and city parking lots within 12 hours.

Three de-icing materials are named: rock salt, which is sodium chloride; liquid calcium chloride at a 32 percent solution; and salt brine. Application rates vary with temperature. That is a materially different chemical load than plain rock salt alone, because calcium chloride stays effective at much lower temperatures than sodium chloride does.

The relevance to private pavement is direct. None of that chemistry stays on the street. It comes up driveways on tires, gets carried into lots on footwear and vehicles, and concentrates in whatever low spots a property has. Chloride solutions depress the freezing point of water, which means the melt-and-refreeze boundary migrates down into the pavement structure instead of staying at the surface. Salt does not dissolve asphalt. It just keeps the water liquid and mobile at temperatures where it would otherwise be locked up as ice, and mobile water finds every open crack.

The ground under the pavement

Champaign County holds the reference locations for two of the most important soil series in Illinois. Drummer, the Illinois state soil, has its typical pedon in Champaign County on the University of Illinois south farm near Urbana. Flanagan, the somewhat better drained series that typically occupies the slightly higher ground beside it, also has its typical pedon in Champaign County. Between them they account for more than a million acres correlated across the region.

Two properties in the table below do most of the work. The first is clay content: Drummer averages 20 to 35 percent clay in the particle-size control section, Flanagan 35 to 42 percent. The second is Flanagan's mineralogy class, smectitic, which names smectite as the dominant clay mineral family. Smectite expands when it takes on water and contracts when it dries, which is the definition of a shrink-swell soil.

The seasonal high water table column is the one most people find surprising. Drummer's official series description records an apparent seasonal high water table from about half a foot above the surface to a foot below it, between January and May in most years. Flanagan carries a perched water table one to two feet below the surface. Champaign pavement is therefore sitting on saturated, volume-changing clay during exactly the months when it is also being freeze-cycled.

How Champaign's own streets are holding up

The city maintains 626 lane miles of roadway. A 2022 analysis of the city's 2020 pavement condition data scored 3,043 Champaign road segments at an average pavement condition index of 66.22, which falls in the fair category, with a predicted following-year average of 61.11. Urbana's 933 segments averaged 56, with a predicted 53, which crosses into the poor category. Urbana's brick streets averaged 60, better than the asphalt around them.

The distribution matters more than the average. In Champaign, 113 segments were rated failed, 351 very poor and 131 serious, which is close to one segment in five. In Urbana the equivalent share was about one in four. Champaign's assistant city engineer summarized the position as not being caught up yet, and described the previous five years as treading water. Urbana's city engineer attributed the condition to deferred maintenance and an unhidden funding gap.

This is the most useful benchmark a private property owner in Champaign has. These are professionally managed pavements, on the same soil, in the same climate, with engineers tracking their condition and a capital program behind them, and roughly a fifth of the network has still slipped into the bottom categories. A driveway or a small commercial lot has none of those advantages. The curve is the same; only the budget and the attention differ.

Sources & Methodology

Every figure above was taken from the primary sources below (accessed 2026-07-25). Where a number is derived (arithmetic on published figures) or covers a broader period or area, the text says so.

1. Illinois State Climatologist - Champaign Climate Normals — 1981-2010 normals for the Champaign Willard Airport and Champaign 9 SW stations. Source for monthly and annual high and low temperatures, days with a low at or below 32F (123.5 a year at Willard, 126.6 at Champaign 9 SW), days at or below 0F (6.1), and days at or above 90F (15.9).
2. Illinois State Climatologist - Averages and Records for Champaign-Urbana — Source for average annual snowfall of 23.2 inches and the monthly snowfall distribution, average annual precipitation of 41.38 inches, average last spring frost of April 15 and first fall frost of October 17, the 109F and -25F records, and the single-storm, snow-depth and seasonal snowfall records. Records date to 1888, snowfall to 1903.
3. City of Champaign - Snow and Ice Removal — The city's own description of winter operations. Source for 14 snow plow trucks, seven primary routes of 19 to 25 miles, primary routes as roughly 50 percent of the street system, the 12 and 24 hour clearing targets, and the three de-icers used: rock salt, 32 percent liquid calcium chloride and salt brine.
4. USDA NRCS - Drummer Official Series Description — The official series description for the Illinois state soil. Source for the typical pedon in Champaign County on the University of Illinois south farm near Urbana, the Typic Endoaquolls classification, poorly drained status, 40 to 60 inches of loess over loamy stratified outwash, 20 to 35 percent clay in the control section, and the January to May seasonal high water table.
5. USDA NRCS - Flanagan Official Series Description — Source for Flanagan's typical pedon in Champaign County, the fine, smectitic, mesic Aquic Argiudolls classification, somewhat poorly drained status, 35 to 42 percent clay in the particle-size control section, and the perched seasonal high water table one to two feet below the surface.
6. CU-CitizenAccess - How bad are the streets of Champaign and Urbana? — Analysis of both cities' 2020 pavement condition data. Source for Champaign's 626 lane miles, the 66.22 average pavement condition index across 3,043 segments, Urbana's 56 across 933 segments, the failed, very poor and serious segment counts, the brick street average of 60, and the city engineers' comments on deferred maintenance.
7. U.S. Census Bureau QuickFacts - Champaign city, Illinois — Source for the July 2025 population estimate of 91,195, 36,815 households, 2.21 persons per household, the 43.8 percent owner-occupied housing unit rate for 2020-2024, median owner-occupied value of $210,900 and median gross rent of $1,123.