Sunday: High pressure will keep southern Wisconsin dry and mild. Southerly winds will develop during the day, becoming breezy but generally staying under 20 mph. High temperatures will reach the mid to upper 60s inland, though it will be cooler near Lake Michigan. Increasing clouds late in the day will signal the approach of the next storm system.
Sunday Night: Clouds will continue to increase overnight as a strong warm air flow moves in. Low temperatures will be mild, holding in the upper 40s to lower 50s. Some scattered showers or isolated storms could develop late, especially toward morning as a warm front lifts northward. Instability could support a few thunderstorms with small hail possible.
Monday: Monday will be warm, windy, and increasingly unsettled. Highs will reach near 80°F inland; mid-60s near the lake. Early showers and storms associated with the warm front are possible, but the main severe threat arrives late Monday afternoon into Monday night as a strong cold front moves in. Severe storms are likely west of Madison (risk level 4/5), with a lower but still notable threat toward the lakeshore (risk 2–3/5). All hazards—damaging winds, hail, and isolated tornadoes—are possible, with the most widespread activity expected during the evening and overnight hours.
Severe Weather Risk: On Monday afternoon and evening, a major severe weather event is expected across the Upper Midwest, including southern Wisconsin. A strong low-pressure system will move eastward from South Dakota into the Upper Great Lakes, while multiple small disturbances travel through the system. This setup will create a highly favorable environment for dangerous thunderstorms.
Early Monday morning, some scattered storms may already be ongoing farther north (in areas like North Dakota and northern Minnesota), but farther south in Wisconsin, atmospheric conditions will be much more supportive of powerful storms later in the day. As warm, moist air from the Gulf of Mexico moves north, the atmosphere will become very unstable. As cooler air moves in higher up during the afternoon, this will allow explosive thunderstorm development.
By late afternoon into the evening, thunderstorms are expected to rapidly form across southern Wisconsin. Early in the event some storms may remain isolated, allowing them to rotate easily and potentially produce very large hail and strong tornadoes. As the evening goes on, the storms are expected to grow into larger clusters and move rapidly eastward, bringing a continued risk of damaging winds and a few tornadoes into the night.
The highest risk for dangerous strong, rotating thunderstorms will be into farther southern Wisconsin before storms merge into clusters later Monday night near Milwaukee. Conditions will remain favorable for all severe weather hazards until the cold front passes early Tuesday morning.
Tuesday-Thursday: Storms should end by early Tuesday morning as the cold front moves east into Lake Michigan and northern Illinois. Wrap-around showers may linger through Tuesday, and cooler northwest winds will develop. Highs will fall back into the 50s and lower 60s. High pressure will bring drier weather Tuesday night into Wednesday, but overnight lows could dip into the mid-30s, raising concerns for frost in some areas. Temperatures will rebound into the 60s later in the week, with another chance for rain developing by Thursday or Friday as another system approaches.
