Historical weather data, all-time temperature records, and monthly climate averages for Round Lake Beach, IL. Explore typical weather conditions by week for trip planning, and see how today compares to the historical record.
April 4th in Round Lake Beach is a coin-flip weather day — temperatures average a mild 55° high but have swung wildly from an 18° freeze in 1995 to a shorts-worthy 76° in 1999. There's a 45% chance of rain, so keep an umbrella handy, though snow is nearly off the table at just 2%.
Round Lake Beach has seen some genuinely brutal extremes over its 78 years of records — from a scorching 101° in July 1995 to a bone-crushing -32° in January 2019, a jaw-dropping 133-degree swing. A single July day in 1985 dumped 4.77 inches of rain, and a February 2011 snowstorm buried the area under 17.3 inches in one shot.
Summers here peak in mid-July with average highs around 83-84°, while January and February are brutally cold with highs barely cracking the upper 20s. If you're planning a visit, late June through early July brings the heaviest rainfall, averaging over an inch a week — summer warmth comes with a price.