Historical weather data, all-time temperature records, and monthly climate averages for Algonquin, IL. Explore typical weather conditions by week for trip planning, and see how today compares to the historical record.
April 4th in Algonquin sits right in that classic spring uncertainty zone — historically, highs average 55° but have swung anywhere from a 17° freeze in 1982 to a shirtsleeves-worthy 78° back in 1921. There's about a 1-in-3 chance of rain today, though the odds of snow are slim at just 3%.
Algonquin's weather has real range — 130 degrees of it, to be exact, stretching from a brutal -27° in January 1985 to a scorching 103° in July 1910. The wettest single day on record dumped 6.47 inches in July 2010, and a January 1966 storm buried the area under 16.5 inches of snow in one shot.
Summer is the sweet spot here, with highs peaking around 84-85° in mid-July before a steady autumn cooldown drops averages to 29° by January. June is the wettest month to watch, averaging over an inch of precipitation in its middle weeks. If you're planning a visit, May through September offers the most comfortable window — anything outside that range means dressing for real Midwest weather.