3 Things To Know:
- Heat and humidity will persist, with heat indices reaching the low to mid-90s.
- Isolated thunderstorms are possible this evening and again Tuesday afternoon.
- Areas of fog could reduce visibility to 2 miles overnight.
As we delve into the early week forecast for Southeast Wisconsin, heat and humidity are the prominent themes. According to the latest National Weather Service (NWS) Area Forecast Discussion, expect afternoon heat index values in the low to mid-90s through Wednesday, with the potential for temperatures to climb into the upper 90s in some areas.
Evening Thunderstorms and Overnight Fog
This afternoon and evening, we might see isolated thunderstorms, particularly toward the southern regions. Chances are not high, but storms could develop as the day progresses. The main threat from any storms will be lightning, but the overall severe threat remains low.
After sunset, temperatures are projected to drop into the low 70s. Calm winds and high humidity will lead to the formation of fog overnight, with areas of dense fog possible in low-lying regions. Visibility could drop to as low as 2 miles.
Tuesday’s Forecast: Heat Build-up
Fog will dissipate by Tuesday morning, paving the way for another hot day. Highs are expected to range from the upper 80s to 90 degrees. Areas nearer the Wisconsin-Illinois border could experience heat index values briefly approaching 100 degrees.
Afternoon thunderstorms may re-emerge, with a 20 to 30 percent chance for isolated to scattered showers and storms. If a storm does develop, it will primarily affect the central and southern parts of the state, bringing additional lightning risks.
Midweek Storm Chances
Looking ahead to late Tuesday night and into Wednesday morning, scattered storms are again possible, particularly for central Wisconsin. The potential for severe weather remains low but should be monitored. As broad low pressure moves into the region, storm chances will increase, especially Wednesday night into Thursday morning.
As stated in the NWS discussion, “…broad low pressure develops in the central Plains…support[ing] a severe threat due to the enhanced CAPE, moisture, and more focused trigger.” This suggests that late-week weather could be dynamic, so keep an eye on updates.
Looking Ahead
Warm and humid weather will persist through the weekend, with high temperatures remaining in the 80s. However, a shift toward more seasonable conditions should start around Friday as high pressure builds in, leading to drier and cooler conditions for the start of next week.
For those venturing outdoors, staying hydrated and being aware of evolving weather conditions is crucial. Keep an eye out for further updates as the week progresses.
For updated forecasts where you live check out our Forecasts Page.
Source: NWS MKX Area Forecast Discussion, issued 2026-08-31T20:36:00+00:00.
