Historical weather data, all-time temperature records, and monthly climate averages for Saint Charles, MO. Explore typical weather conditions by week for trip planning, and see how today compares to the historical record.
April 5 in Saint Charles runs mild on average — a 62° high and 40° low — but history shows the date has plenty of range. Temperatures have swung from a bitter 17° in 1920 all the way to a shirt-sleeve 89° in 1954, so don't put away that jacket just yet. There's about a 1-in-3 chance of rain today, though snow is nearly off the table at just 1%.
Saint Charles has seen some genuinely extreme weather over its 130-plus years of records. The mercury has soared to 115° in July 1954 and plunged to -25° in January 1894 — a jaw-dropping 140-degree range. A single July day in 2022 dropped 9.2 inches of rain, and a March 1912 storm buried the area under a foot of snow.
Saint Charles peaks in heat the week of July 9–15, when average highs hit 90°, and bottoms out in early January around a chilly 40°. Spring is the wettest stretch — mid-May averages over an inch of rain in a single week — so pack accordingly if you're visiting then. Fall offers the sweetest shoulder season, with October highs in the 70s and much drier conditions.