National Weather Service Forecast for: Janesville WI
Issued by: National Weather Service Milwaukee, WI
Updated: 4:52 am CDT Jun 30, 2026
 
Today

Today: Mostly sunny and hot, with a high near 93. Heat index values as high as 105. Southwest wind 10 to 15 mph, with gusts as high as 25 mph.
Hot

 Tonight

Tonight: Mostly clear, with a low around 75. Southwest wind 10 to 15 mph.
Mostly Clear

 Wednesday

Wednesday: Sunny and hot, with a high near 93. Heat index values as high as 103. Southwest wind 10 to 15 mph.
Hot

 Wednesday
Night
Wednesday Night: A 20 percent chance of showers and thunderstorms after 1am. Mostly clear, with a low around 75. Southwest wind 10 to 15 mph.
Mostly Clear
then Slight
Chance
T-storms
 Thursday

Thursday: A 30 percent chance of showers and thunderstorms after 1pm. Mostly sunny and hot, with a high near 91. Southwest wind around 10 mph.
Mostly Sunny
then Chance
T-storms
 Thursday
Night
Thursday Night: A chance of showers and thunderstorms, then showers likely and possibly a thunderstorm after 1am. Mostly cloudy, with a low around 72. Southwest wind around 5 mph becoming calm in the evening. Chance of precipitation is 70%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.
Chance
T-storms then
Showers
Likely
 Friday

Friday: Showers likely and possibly a thunderstorm. Partly sunny, with a high near 88. Southwest wind 5 to 10 mph. Chance of precipitation is 60%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.
Showers
Likely

 Friday
Night
Friday Night: Showers likely and possibly a thunderstorm before 1am, then a chance of showers and thunderstorms after 1am. Partly cloudy, with a low around 69. Southwest wind around 5 mph becoming calm in the evening. Chance of precipitation is 60%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.
Showers
Likely

 Independence
Day
Independence Day: A 50 percent chance of showers and thunderstorms. Partly sunny, with a high near 88.
Chance
Showers then
Chance
T-storms
Hi 93 °F Lo 75 °F Hi 93 °F Lo 75 °F Hi 91 °F Lo 72 °F Hi 88 °F Lo 69 °F Hi 88 °F

Hazardous Weather Outlook
Extreme Heat Warning
 

Today
 
 Mostly sunny and hot, with a high near 93. Heat index values as high as 105. Southwest wind 10 to 15 mph, with gusts as high as 25 mph.
Tonight
 
 Mostly clear, with a low around 75. Southwest wind 10 to 15 mph.
Wednesday
 
 Sunny and hot, with a high near 93. Heat index values as high as 103. Southwest wind 10 to 15 mph.
Wednesday Night
 
 A 20 percent chance of showers and thunderstorms after 1am. Mostly clear, with a low around 75. Southwest wind 10 to 15 mph.
Thursday
 
 A 30 percent chance of showers and thunderstorms after 1pm. Mostly sunny and hot, with a high near 91. Southwest wind around 10 mph.
Thursday Night
 
 A chance of showers and thunderstorms, then showers likely and possibly a thunderstorm after 1am. Mostly cloudy, with a low around 72. Southwest wind around 5 mph becoming calm in the evening. Chance of precipitation is 70%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.
Friday
 
 Showers likely and possibly a thunderstorm. Partly sunny, with a high near 88. Southwest wind 5 to 10 mph. Chance of precipitation is 60%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.
Friday Night
 
 Showers likely and possibly a thunderstorm before 1am, then a chance of showers and thunderstorms after 1am. Partly cloudy, with a low around 69. Southwest wind around 5 mph becoming calm in the evening. Chance of precipitation is 60%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.
Independence Day
 
 A 50 percent chance of showers and thunderstorms. Partly sunny, with a high near 88.
Saturday Night
 
 A 50 percent chance of showers and thunderstorms. Mostly cloudy, with a low around 66.
Sunday
 
 A 30 percent chance of showers and thunderstorms. Partly sunny, with a high near 86.
Sunday Night
 
 A 20 percent chance of showers and thunderstorms. Partly cloudy, with a low around 64.
Monday
 
 A 20 percent chance of showers and thunderstorms. Mostly sunny, with a high near 85.

 

Forecast from NOAA-NWS for Janesville WI.