Lake St. Louis, MO climate
Lake St. Louis has chilly winters and warm summers. A typical July afternoon reaches 88°, a January night drops to 22°, and about 14 inches of snow falls in a normal winter.
NOAA 1991-2020 climate normals Updated once a decade10° warmer than normal today. The forecast high is 84°, and a typical Oct 1 in Lake St. Louis peaks around 74°.Live forecast: National Weather Service · Normal: NOAA 1991–2020
What a year in Lake St. Louis feels like
Winter
Spring
Summer
Fall
Lake St. Louis weather by month
Average highs, lows, rain and snow for every month, from NOAA’s 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 40° | 22° | 2.5" | 4.1" | 8 | 5 | 25° – 42° |
| February | 45° | 26° | 2.3" | 3.7" | 8 | 4 | 25° – 45° |
| March | 56° | 34° | 3.6" | 1.7" | 10 | 1 | 37° – 58° |
| April | 67° | 44° | 4.7" | 0.2" | 10 | 0 | 49° – 61° |
| May | 76° | 54° | 5.0" | 0 | 13 | 0 | 60° – 73° |
| June | 84° | 63° | 4.5" | 0 | 10 | 0 | 69° – 78° |
| July | 88° | 68° | 3.8" | 0 | 8 | 0 | 73° – 85° |
| August | 87° | 65° | 3.7" | 0 | 8 | 0 | 70° – 82° |
| September | 80° | 57° | 3.4" | 0 | 7 | 0 | 64° – 75° |
| October | 69° | 46° | 3.2" | 0 | 9 | 0 | 52° – 63° |
| November | 55° | 35° | 3.5" | 0.8" | 8 | 1 | 37° – 52° |
| December | 44° | 27° | 2.6" | 3.0" | 8 | 4 | 21° – 43° |
| Year | 66° | 45° | 42.7" | 13.5" | 107 | 15 |
“Wet days” have at least 0.01" of rain or melted snow. “Snow on ground” counts days with 1" or more. The 30-year range is the coldest and warmest that month’s average temperature got between 1991 and 2020.
Rain and snow in Lake St. Louis
Lake St. Louis gets 43 inches of rain and melted snow a year. May is the wettest month and February the driest. Rain or snow falls on about 107 days a year. Snow covers the ground about 15 days of the year.
About 199 frost-free days a year
In half of years the last 32° night comes by April 10 and the first one by October 26. That leaves about 199 frost-free days for gardens, longer than 72% of U.S. towns.
Heating and cooling a home in Lake St. Louis
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In Lake St. Louis, 79% of that work is heating and 21% is cooling.
Degree days measure how far each day’s average temperature falls below or rises above 65°, added up over a year. Source: NOAA station normals.
Lake St. Louis and its neighbors
Lake St. Louis borders 3 towns with climate data. January nights across them vary by 0.6°. Wentzville has the coldest January nights (22°) and Dardenne Prairie the hottest July afternoons (88°). Lake St. Louis’s January low is 22° and its July high 88°.
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value.
How Lake St. Louis compares
Compared with every U.S. town and city on TownTapestry, each counted once.
Warmer than it used to be
The last 30 years in Lake St. Louis averaged 1.0° warmer than the 1900s. The biggest change is in December (+2.3°). The shift is smaller than in 68% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at Lake St. Louis’s spot on NOAA’s grid
How much a month can swing
A normal is an average, and real years wander around it. December swings the most: between 1991 and 2020 its average temperature ranged from 21° to 43°. June is the most reliable, staying within 9°.
Common questions about Lake St. Louis’s climate
What is the coldest month in Lake St. Louis?
January, with a typical high of 40° and a low of 22°.
What is the hottest month in Lake St. Louis?
July, with a typical high of 88° and a low of 68°. About 36 days a year reach 90°.
How much snow does Lake St. Louis get?
About 14 inches in a normal winter, most of it in January.
When is the first frost in Lake St. Louis?
In half of years the first 32° night comes by October 26, and the last spring frost by April 10.
What is the rainiest month in Lake St. Louis?
May, with 5.0 inches of rain and melted snow. The year totals 43 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for Lake St. Louis itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Weldon Spring Nws, MO (8 mi) away. Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000.