National Oceanic and Atmospheric Administration National Weather Service United States Department of Commerce
Current conditions at

Sparta, Sparta / Fort McCoy Airport (KCMY)

Lat: 43.96°NLon: 90.74°WElev: 837ft.

A Few Clouds

81°F

27°C

Humidity 68%
Wind Speed Calm
Barometer 29.84 in (1010.3 mb)
Dewpoint 69°F (21°C)
Visibility 10.00 mi
Heat Index84°F (29°C)
Last update 30 Aug 1:55 pm CDT
Extended Forecast for

Ontario WI

  • This Afternoon

    This Afternoon: A 30 percent chance of showers and thunderstorms before 3pm. Partly sunny, with a high near 87. South wind around 9 mph.

    High: 87 °F

    Chance
    Showers

  • Tonight

    Tonight: Mostly cloudy, with a low around 72. South wind 5 to 7 mph, with gusts as high as 18 mph.

    Low: 72 °F

    Mostly Cloudy

  • Monday

    Monday: Mostly cloudy, then gradually becoming sunny, with a high near 90. Heat index values as high as 98. Southwest wind 6 to 9 mph, with gusts as high as 18 mph.

    High: 90 °F

    Decreasing
    Clouds

  • Monday Night

    Monday Night: A slight chance of showers and thunderstorms between 3am and 4am. Partly cloudy, with a low around 68. Light and variable wind. Chance of precipitation is 20%.

    Low: 68 °F

    Partly Cloudy
    then Slight
    Chance
    T-storms

  • Tuesday

    Tuesday: Partly sunny, with a high near 90. Calm wind becoming southwest around 5 mph in the afternoon.

    High: 90 °F

    Partly Sunny

  • Tuesday Night

    Tuesday Night: A 40 percent chance of showers and thunderstorms after 1am. Mostly cloudy, with a low around 68. Calm wind. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

    Low: 68 °F

    Mostly Cloudy
    then Chance
    Showers

  • Wednesday

    Wednesday: A 20 percent chance of showers and thunderstorms before 1pm. Partly sunny, with a high near 88. Light and variable wind.

    High: 88 °F

    Slight Chance
    T-storms

  • Wednesday Night

    Wednesday Night: A 50 percent chance of showers and thunderstorms, mainly after 1am. Partly cloudy, with a low around 65. Calm wind.

    Low: 65 °F

    Slight Chance
    T-storms then
    Chance
    T-storms

  • Thursday

    Thursday: A 30 percent chance of showers and thunderstorms before 1pm. Partly sunny, with a high near 84. Light south wind.

    High: 84 °F

    Chance
    T-storms

Detailed Forecast

This Afternoon
A 30 percent chance of showers and thunderstorms before 3pm. Partly sunny, with a high near 87. South wind around 9 mph.
Tonight
Mostly cloudy, with a low around 72. South wind 5 to 7 mph, with gusts as high as 18 mph.
Monday
Mostly cloudy, then gradually becoming sunny, with a high near 90. Heat index values as high as 98. Southwest wind 6 to 9 mph, with gusts as high as 18 mph.
Monday Night
A slight chance of showers and thunderstorms between 3am and 4am. Partly cloudy, with a low around 68. Light and variable wind. Chance of precipitation is 20%.
Tuesday
Partly sunny, with a high near 90. Calm wind becoming southwest around 5 mph in the afternoon.
Tuesday Night
A 40 percent chance of showers and thunderstorms after 1am. Mostly cloudy, with a low around 68. Calm wind. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.
Wednesday
A 20 percent chance of showers and thunderstorms before 1pm. Partly sunny, with a high near 88. Light and variable wind.
Wednesday Night
A 50 percent chance of showers and thunderstorms, mainly after 1am. Partly cloudy, with a low around 65. Calm wind.
Thursday
A 30 percent chance of showers and thunderstorms before 1pm. Partly sunny, with a high near 84. Light south wind.
Thursday Night
A 40 percent chance of showers and thunderstorms. Partly cloudy, with a low around 65. Calm wind.
Friday
A 20 percent chance of showers and thunderstorms. Mostly sunny, with a high near 85. Calm wind becoming southeast around 5 mph in the afternoon.
Friday Night
A 20 percent chance of showers and thunderstorms. Mostly clear, with a low around 64. Calm wind.
Saturday
Mostly sunny, with a high near 86. Calm wind becoming east around 5 mph in the afternoon.
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ABOUT THIS FORECAST

 
Point Forecast:
Ontario WI
 43.73°N 90.58°W
Last Update:
1:26 pm CDT Aug 30, 2026
Forecast Valid:
2pm CDT Aug 30, 2026-6pm CDT Sep 5, 2026
 
Forecast Discussion
 
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Additional Resources

Radar & Satellite Image

Link to Local Radar Data Link to Satellite Data

Hourly Weather Forecast

National Digital Forecast Database

National Digital Forecast Database Maximum Temperature Forecast

High Temperature

National Digital Forecast Database Weather Element Forecast

Chance of Precipitation