Storm Record · Columbia, Dane, Dodge, Jefferson, Sauk, Walworth, Waukesha Counties
July 20, 2006: Straight-line wind across seven counties
What the National Weather Service recorded
During the pre-dawn early morning hours of July 20th, a severe squall line pushed into south-central and southeast Wisconsin from southern Minnesota. This squall line produced mainly damaging winds, some reports being "significant" (>65 knots or hurricane-force), and only a couple hail reports. One of the significant reports was at a location 4 miles northeast of Monona at 0140CST where a gust of 71 knots (82 mph) was measured, before the power went out. Hundreds of trees were knocked down in the Madison area, and there were dozens power-line damage reports. Up to 40,000 customers lost electrical power across southern Wisconsin, with 13,000 alone in the Madison area. The squall line weakened as it approached the corner of southeast Wisconsin due to weakening instability, despite still favorable deep layer shear. Toward dawn, more scattered thunderstorms developed across south-central Wisconsin as a northwest to southeast axis of instability redeveloped. A few of these storms pulsed up to produce only marginal severe hail and wind.
Source: NOAA Storm Events Database · episode 1215740
Every report, in the Weather Service's words
Where It Hit
| Location | County | Hazard | Size | Report |
|---|---|---|---|---|
| Monona (4 NE) | Dane | Wind | 82 mph wind | Hurricane force wind gusts to 71 knots (82 mph) produced tree and power line damage 4.0 miles northeast of Monona. |
| Madison (5 W) | Dane | Wind | 75 mph wind | Bricks were taken off a building in downtown Madison due to severe, hurricane-force wind gusts to an estimated 65 knots (75 mph). Dozens of power-lines were damaged. At least 3 vehicles were either damaged or destroyed by fallen trees. Many roads were blocked by the tree debris. A large tree was toppled onto a home on the near east side of Madison, resulting in minor roof damage. |
| La Valle | Sauk | Wind | 75 mph wind | Trees and power lines reported down countywide. |
| Waterloo | Jefferson | Wind | 64 mph wind | Trees and power lines down. |
| Rome | Jefferson | Wind | 64 mph wind | Tree down. |
| Albion (3 ESE) | Dane | Wind | 64 mph wind | Trees down. One large tree fell on a home's roof, resulting in minor damage. |
| Blue Mounds | Dane | Wind | 64 mph wind | Trees and power-lines down. |
| Ft Atkinson | Jefferson | Wind | 64 mph wind | Trees toppled over. Two small planes at the Ft. Atkinson Municipal Airport broke loose from their morrings due to the powerful winds. One of the plane's wings were damaged as it tipped from side to side. |
| Portage | Columbia | Wind | 64 mph wind | Trees toppled and some power-lines downed. |
| Portland (2 NNW) | Dodge | Wind | 64 mph wind | Trees and power lines down. |
| Pardeeville | Columbia | Wind | 64 mph wind | |
| Dousman (4 SSW) | Waukesha | Wind | 60 mph wind | Tree limbs and trees down. |
| Brookfield | Waukesha | Wind | 60 mph wind | Power lines down. |
| Belleville | Dane | Wind | 60 mph wind | Large tree branches and power lines down. |
| Darien | Walworth | Wind | 60 mph wind | Trees and power lines down. |
| Sun Prairie (4 NNE) | Dane | Wind | 60 mph wind | Trees down. |
| Theresa (4 W) | Dodge | Wind | 60 mph wind | Trees down. |
| Blue Mounds (5 S) | Dane | Wind | 60 mph wind | Tree and tree branches down. |
| Lake Geneva (2 E) | Walworth | Wind | 60 mph wind | Trees and power lines down. |
| Wisconsin Dells (2 ESE) | Columbia | Wind | 60 mph wind | |
| Pardeeville (4 W) | Columbia | Hail | 0.88" hail | |
| Madison (5 NW) | Dane | Hail | 0.75" hail |
Service areas this storm touched