Wisconsin extreme heat; storms expected through July 4 weekend

MILWAUKEE - Wisconsin's dangerous stretch of heat and humidity will begin to ease later this week, but the tradeoff will be a much more active weather pattern as we head toward the Fourth of July weekend. 

While temperatures remain well above normal through the end of the workweek, several rounds of thunderstorms could bring damaging winds, large hail, heavy rainfall and lightning. 

Anyone with outdoor holiday plans will want to keep a close eye on the forecast as the timing of individual storm complexes becomes clearer over the next few days.

Heat remains a concern

What we know:

The Extreme Heat Warning expires Wednesday evening, but the hot and humid air isn't going anywhere just yet. Heat index values will continue reaching to near 100 degrees or higher Wednesday, Thursday and Friday, and additional heat headlines may still be needed depending on how much cloud cover and thunderstorm activity develops.

The combination of hot afternoons and warm, muggy nights continues to increase the risk of heat-related illnesses, especially for anyone spending extended time outdoors.

Multiple rounds of storms expected

What's next:

The same weather pattern responsible for the heat will also fuel several opportunities for thunderstorms through the holiday weekend. Storms are expected to develop in waves rather than as one continuous event. 

The greatest concern is that each round could produce:

• Damaging wind gusts
• Large hail
• Torrential rainfall
• Frequent cloud-to-ground lightning

Forecast confidence is high that thunderstorms will occur. The challenge is determining exactly when and where each complex will develop and to what extent they become severe. As the week progresses, model data will sharpen and we will have a better track and timing. Please check back frequently for updates.

Fourth of July remains unsettled

Holiday Forecast:

Saturday currently appears to be the most active day of the holiday weekend as a slow-moving frontal boundary combined with abundant moisture and daytime heating creates favorable conditions for additional showers and thunderstorms. Some storms could become strong to severe while producing locally heavy rainfall. Even storms that remain below severe limits will still pose a significant lightning threat for outdoor celebrations, festivals, parades and fireworks displays.

Sunday also carries a chance for thunderstorms, although exactly where they develop will depend on where Saturday's front ultimately settles.

Looking ahead

What's next:

The overall pattern finally begins to improve early next week. H

igh pressure is expected to gradually build into the western Great Lakes, allowing rain chances to decrease while temperatures become a bit more comfortable compared to this week's dangerous heat. While it won't be completely cool, the oppressive heat should slowly ease as Wisconsin moves into a more typical early July weather pattern.

WeatherSevere Weather