ROCKFORD, IL — Another round of heavy rain is heading for northern Illinois and southern Wisconsin. After a review of a wide range of computer model guidance, forecasters are highly confident the region will get very healthy rainfall over the next few days. NOAA’s Weather Prediction Center has placed the entire Stateline area under a Level 2 out of 4 risk for excessive rainfall on both Wednesday and Thursday. Remnant moisture from Hurricane Polo is combining with an approaching cold front to bring widespread soaking rain for much of both days and nights. Rockford is also on the edge of a spot in the Top 10 wettest Septembers on record.
Level 2 Excessive Rain Risk Covers the Stateline
The Weather Prediction Center’s excessive rainfall outlook for Wednesday and Wednesday night puts most of northern Illinois, southern Wisconsin and eastern Iowa under a Level 2 of 4 risk. That includes Rockford, Freeport, Dixon, Rochelle, DeKalb, Harvard, Beloit, Janesville, Monroe, Galena, Dubuque and Clinton. Areas farther east, including Elgin, Aurora and parts of the Chicago suburbs, are under a lower Level 1 risk.
A similar outlook is in place for Thursday and Thursday night, with most of the Stateline again under a Level 2 risk. Repeated rain on back-to-back days raises the chance of standing water and localized flooding, especially where the ground is already saturated from a wet September.
Two to Three Inches Expected Through Early Friday
The latest National Blend of Models keeps showing a broad swath of 2 to 3 inches of rain across nearly all of northern Illinois and southern Wisconsin through early Friday morning. In setups like this, forecasters usually don’t favor any one model. A blend of all the solutions tends to land closest to reality.
Along the Mississippi River, projected totals are among the highest in the region. Savanna is near 3.49 inches, Clinton about 3.33 inches, and Maquoketa, Cascade and Davenport around 3.26 inches. Bellevue and Walnut are near 2.81 inches, and Dubuque is about 2.66 inches.
Rockford, Freeport and Dixon Near 3 Inches
Across the heart of northern Illinois, the blend shows totals close to 3 inches. Rockford, Freeport and Dixon are each projected near 2.95 inches, while Rochelle and Harvard are around 2.88 inches. Mendota is near 2.53 inches, and DeKalb and Round Lake Beach are about 2.46 inches.
Farther east, totals taper slightly. Elgin is projected near 2.26 inches, Aurora around 2.13 inches and Joliet close to 1.89 inches. Even at the low end of the range, that’s still a significant amount of rain over a short period.
Southern Wisconsin Also in Line for a Soaking
In southern Wisconsin, Beloit and Monroe are projected near 2.6 inches, with Janesville around 2.46 inches. Darlington and Delavan are near 2.26 inches, Burlington about 2.13 inches, and Platteville around 2.07 inches. Farther north, Waukesha is near 2.01 inches, Madison about 1.89 inches and Milwaukee close to 1.77 inches.
With this much rain across Rock, Green, Walworth and Lafayette counties, residents should be ready for wet roads, slower commutes and water collecting in low spots.
Standing Water and Ponding Expected
With 2 to 3 inches falling across the region, it wouldn’t take much for standing water to build up in low-lying areas. Ponding on roadways is likely to be a problem again in spots, especially on streets with poor drainage, underpasses and rural roads near creeks and ditches.
Drivers should slow down, watch for hydroplaning and never drive through water of unknown depth. Homeowners should clear gutters, downspouts and storm drains, and check that sump pumps are working before the heaviest rain arrives.
Rockford Closing In on a Top 10 Wettest September
Rockford has officially recorded 6.45 inches of rain so far in September. If another 1.48 inches falls before 11:59 p.m. Wednesday, September 2026 will rank among the Top 10 wettest Septembers on record for the city. With the forecast calling for close to 3 inches through early Friday, that milestone looks well within reach. October is also set to start with plenty more rain.
For continuing coverage of heavy rain in northern Illinois, southern Wisconsin and weather developments across the United States, visit diamondprowl.com.
