McHenry County, IL: Current UV Index and Hourly Forecast

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As of 10:28 AM CDT on March 20, 2026, all 40 cities in McHenry County, IL in our database have a UV Index reading of Low. The city with the highest UV Index reading right now is Crystal Lake, IL with a reading of 1.8.

Over the next 24 hours, the highest UV Index reading in McHenry County, IL is expected to be 4.4 in Chemung between 1:00 PM - 2:00 PM CDT today.

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Current UV Index in Cities in McHenry County, IL

• Alden - 1.8
• Algonquin - 1.8
• Big Foot Prairie - 1.8
• Bull Valley - 1.8
• Burtons Bridge - 1.8
• Cary - 1.8
• Chemung - 1.8
• Coral - 1.8
• Crystal Lake - 1.8
• Fox River Grove - 1.8
• Franklinville - 1.8
• Greenwood - 1.8
• Harmony - 1.8
• Hartland - 1.8
• Harvard - 1.8
• Hebron - 1.8
• Holiday Hills - 1.8
• Huntley - 1.8
• Island Lake - 1.8
• Johnsburg - 1.8
• Lake in the Hills - 1.8
• Lakemoor - 1.8
• Lakewood - 1.8
• Lawrence - 1.8
• Marengo - 1.8
• McCullom Lake - 1.8
• McHenry - 1.8
• Oakwood Hills - 1.8
• Pistakee Highlands - 1.8
• Prairie Grove - 1.8
• Richmond - 1.8
• Ridgefield - 1.8
• Riley - 1.8
• Ringwood - 1.8
• Solon Mills - 1.8
• Spring Grove - 1.8
• Trout Valley - 1.8
• Union - 1.8
• Wonder Lake - 1.8
• Woodstock - 1.8