MADISON, Wisconsin — A significant and potentially life-threatening flash flooding emergency is unfolding overnight across southeast Minnesota, northeast Iowa, southern Wisconsin and northern Illinois, with heavy thunderstorms training over the same areas repeatedly and rainfall rates reaching 2 to 2.5 inches per hour. Portions of southeast Minnesota have already received 4 to 6 inches of rainfall and locally another 4 to 6 plus inches could fall where storms continue tracking over the same locations through dawn Saturday, September 20, 2026. Considerable to locally significant flash flooding is expected — this is a dangerous and potentially life-threatening situation for anyone near urban areas, low-lying roads, creeks, streams and flood-prone locations across the affected region. Do not drive through flooded roads. Turn Around, Don’t Drown.
This Is a Life-Threatening Situation Right Now
The source data uses the clearest possible language — a threat for significant and life-threatening urban flooding impacts will exist across the flash flooding zone through dawn Saturday. This is not routine overnight rain. The combination of 2 to 2.5 inch per hour rainfall rates, storms training repeatedly over the same locations and a powerful 30 to 40 plus knot low-level jet continuously feeding deep moisture and instability into the storm system creates conditions where water can rise from nothing to life-threatening levels in minutes. If you are in southeast Minnesota, southern Wisconsin, northeast Iowa or northern Illinois and water is rising near your location right now, move to higher ground immediately.
Why These Storms Keep Hitting the Same Areas
The source data identifies the mechanism driving the most dangerous aspect of tonight’s flooding — a strong 30 to 40 plus knot low-level jet is continuously feeding deep moisture and instability into the storms, allowing them to regenerate and train over the same areas rather than moving on. Training storms are the most flood-dangerous storm pattern that exists because each new cell drops heavy rainfall on ground that is already saturated and overwhelmed from the previous cell. With rainfall rates of 2 to 2.5 inches per hour and storms continuously regenerating, there is no recovery time for the affected areas between storm cells tonight.
Where the Flooding Threat Is Most Concentrated
The flash flooding map, valid as of 5:30 AM UTC Saturday, September 19, 2026, shows the considerable flash flooding zone outlined in pink covering the following communities:
- Preston, Minnesota is visible within the considerable flash flooding zone on the map, sitting in southeast Minnesota where 4 to 6 inches of rain has already fallen with more on the way through dawn Saturday.
- Boscobel, Wisconsin falls within the considerable flash flooding zone on the map, located in southwest Wisconsin where the most dangerous training storm pattern is focused overnight.
- Madison, Wisconsin is starred on the flash flooding map within the considerable flash flooding zone, confirming this major Wisconsin city is directly inside the life-threatening urban flooding threat area through dawn Saturday, September 20, 2026.
- Milwaukee, Wisconsin is starred on the flash flooding map within the considerable flash flooding zone, placing one of Wisconsin’s largest cities at serious flash flooding risk overnight into Saturday morning.
- The pink outlined zone extends across south-central Wisconsin connecting Preston, Boscobel, Madison and Milwaukee, confirming the considerable flash flooding threat spans a wide corridor across the region through dawn Saturday.
Northern Illinois: Flash Flood Threat Increasing Near Dawn Saturday
If you are in northern Illinois — including the Chicago metro area — the situation is about to get more serious. The axis of heavy rainfall may begin shifting farther south toward northern Illinois around dawn Saturday, increasing the flash flood threat during the early morning hours of Saturday, September 20, 2026. Residents in northern Illinois who thought they were ahead of tonight’s worst rainfall should be prepared for conditions to deteriorate quickly near dawn as the training storm axis shifts southward.
What Totals Are Already on the Ground
- Southeast Minnesota has already received 4 to 6 inches of rainfall before tonight’s additional rounds, meaning the ground is completely saturated and has no capacity to absorb any additional rainfall. Every drop that falls from this point forward runs off immediately into streets, streams and rivers.
- Locally another 4 to 6 plus inches could fall where storms repeatedly track over the same locations through dawn Saturday, September 20, 2026, potentially bringing some spots to 8 to 12 inch cumulative totals — a catastrophic amount for any community regardless of drainage infrastructure.
- Rainfall rates of 2 to 2.5 inches per hour are occurring in the most intense storm cores, a rate severe enough to overwhelm any urban drainage system in the country within 30 to 60 minutes of sustained rainfall at that intensity.
Do Not Drive Through Flooded Roads Tonight
The source data issues a clear and urgent warning — Do Not Drive Through Flooded Roads. Turn Around, Don’t Drown. Conditions can deteriorate very quickly overnight across southeast Minnesota, southern Wisconsin, northeast Iowa and northern Illinois. The majority of flash flood fatalities occur in vehicles. Just 12 inches of moving water can carry away a standard vehicle and 6 inches of moving water can knock a person off their feet. If you encounter any water covering a roadway tonight, turn around immediately and find an alternate route or wait in a safe location until the flooding recedes.
Emergency Actions to Take Right Now
If you are in Madison, Milwaukee, Preston, Boscobel or any surrounding community in southeast Minnesota, southern Wisconsin or northeast Iowa right now, take these actions immediately:
- Move to the highest floor of your home if water is rising outside.
- Do not enter a basement or low-lying area of your home if flooding is possible.
- Stay off all roads until daylight and until local authorities confirm it is safe to travel.
- If you are in a vehicle and water begins rising around you, exit the vehicle immediately and move to higher ground.
- Call 911 immediately if you or someone near you is in immediate danger from rising water.
