Historical weather data, all-time temperature records, and monthly climate averages for Summit, IL. Explore typical weather conditions by week for trip planning, and see how today compares to the historical record.
April 5 in Summit runs mild but unpredictable — expect a high around 55° and a low near 37°, though this date has swung anywhere from 24° (2018) to 78° (2021). There's a 36% chance of rain, so keep an umbrella handy, but snow is effectively off the table.
Summit's weather has real teeth: the thermometer has climbed to 104° in July 1999 and crashed to -22° in January 2019 — a 126-degree spread over the last three decades. A single October day in 2017 dropped 5.2 inches of rain, and December 2000 buried the area under 14.3 inches of snow.
Summer is Summit's warmest stretch, peaking mid-July with average highs of 86°, while mid-January bottoms out around 30°. Spring is the wettest season — the week of May 7–13 averages over an inch of precipitation. For the most reliable weather, late summer through early fall (August–September) offers warm temps with easing rainfall.