Historical weather data, all-time temperature records, and monthly climate averages for McHenry, IL. Explore typical weather conditions by week for trip planning, and see how today compares to the historical record.
April 5th in McHenry sits right at that awkward shoulder season — the average high is only 51° with lows still dipping to freezing. It's not a date to trust: the thermometer has swung anywhere from a brutal 14° in 1995 to a downright pleasant 75° in 2021. There's a 1-in-3 chance of some precipitation today, though snow is unlikely at just 5%.
McHenry earns its Midwest stripes with a staggering 133-degree spread between its all-time records — from 101° in July 1995 down to -32° on a punishing January day in 2019. Summer storms can be serious here too, with nearly 5 inches of rain falling in a single day back in 1985, and a 17.3-inch snowstorm in February 2011 that still stands as the single-day snow record.
Peak summer comfort runs mid-July through late August, when average highs settle in the low-to-mid 80s — the week of July 16–22 is statistically the warmest of the year at 84°. Winters are genuinely cold, with January highs averaging just 29°, making the stretch from mid-January through February the season to avoid if you're sensitive to the cold. Late June into early July is the wettest stretch, so pack accordingly if you're visiting for summer festivities.