McHenry County, IL: Current UV Index and Hourly Forecast

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As of 12:34 PM CDT on September 11, 2025, all 40 cities in McHenry County, IL in our database have a UV Index reading of High. The city with the highest UV Index reading right now is Crystal Lake, IL with a reading of 5.8.

Over the next 24 hours, the highest UV Index reading in McHenry County, IL is expected to be 6.2 in Crystal Lake between 1:00 PM - 2:00 PM CDT today.

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Current UV Index in Cities in McHenry County, IL

• Alden - 5.7
• Algonquin - 5.8
• Big Foot Prairie - 5.7
• Bull Valley - 5.8
• Burtons Bridge - 5.8
• Cary - 5.8
• Chemung - 5.7
• Coral - 5.8
• Crystal Lake - 5.8
• Fox River Grove - 5.8
• Franklinville - 5.8
• Greenwood - 5.7
• Harmony - 5.8
• Hartland - 5.8
• Harvard - 5.7
• Hebron - 5.7
• Holiday Hills - 5.8
• Huntley - 5.8
• Island Lake - 5.8
• Johnsburg - 5.7
• Lake in the Hills - 5.8
• Lakemoor - 5.8
• Lakewood - 5.8
• Lawrence - 5.7
• Marengo - 5.8
• McCullom Lake - 5.8
• McHenry - 5.8
• Oakwood Hills - 5.8
• Pistakee Highlands - 5.7
• Prairie Grove - 5.8
• Richmond - 5.7
• Ridgefield - 5.8
• Riley - 5.7
• Ringwood - 5.7
• Solon Mills - 5.7
• Spring Grove - 5.7
• Trout Valley - 5.8
• Union - 5.8
• Wonder Lake - 5.7
• Woodstock - 5.8