Historical weather data, all-time temperature records, and monthly climate averages for Waterloo, IL. Explore typical weather conditions by week for trip planning, and see how today compares to the historical record.
April 5th in Waterloo runs the full gamut — this date has seen a scorching 89° in 1967 and a teeth-chattering 24° low back in 1970. A typical April 5th lands around 62° for the high and 38° overnight, with about a 1-in-3 chance of rain. Snow is possible but rare, showing up only 2% of the time.
Waterloo's weather has real range — from a brutal -27° in January 1977 to a sweltering 110° in July 1980, a 137-degree spread that puts this southwestern Illinois town firmly in the 'four serious seasons' category. The wettest single day on record dumped 6.2 inches in September 2018, and a February 1966 snowstorm buried the area under 9 inches in one shot.
Summer is the main event here, with mid-July highs averaging 90° and the mercury staying in the upper 80s through August. If you're cold-averse, avoid early January when average highs sit at just 40°. Late April is the wettest stretch of the year, averaging 1.28 inches of precipitation in a single week.