Historical weather data, all-time temperature records, and monthly climate averages for Lake Saint Louis, MO. Explore typical weather conditions by week for trip planning, and see how today compares to the historical record.
April 5th in Lake Saint Louis runs mild on paper — a 60° high and 38° low on average — but the date has a wild range hiding underneath. The thermometer has swung from a frigid 21° in 1975 to a summery 85° in 2010, a 64-degree spread that captures Midwest spring in a nutshell. There's about a 1-in-3 chance of rain today, but you can put the snow shovel away.
Lake Saint Louis weather doesn't mess around at the extremes. The all-time high of 109° in August 2000 and an all-time low of -28° in December 1989 give this location a jaw-dropping 137-degree range across its recorded history. A single day in December 2015 dropped 6.39 inches of rain, and a February 1984 snowstorm buried the area under 14 inches.
Summer is the main event here, with highs averaging 89° during the peak week of July 16–22, while mid-January bottoms out around a raw 37°. If you're chasing dry weather for a visit, avoid late April through early May — that's the wettest stretch of the year, averaging over an inch of precipitation in a single week. Spring and fall offer the most comfortable travel windows, with April highs in the upper 60s and October near 69°.