Weather Averages in St Louis
For climate and temperatures, here’s a quick breakdown. St. Louis lies in the transitional zone between the humid continental climate type and the humid subtropical climate type (Köppen Dfa and Cfa, respectively), with neither large mountains nor large bodies of water to moderate its temperature. The city experiences hot, humid summers, and chilly to cold winters. It is subject to both cold Arctic air and hot, humid tropical air from the Gulf of Mexico. The average annual temperature recorded at nearby Lambert–St. Louis International Airport, is 57.1 °F (13.9 °C). Both 100 and 0 °F (38 and −18 °C) temperatures can be seen on an average 2 or 3 days per year. Average annual precipitation is about 41.0 inches (1,040 mm), but annual precipitation has ranged from 20.59 in (523 mm) in 1953 to 61.24 in (1,555 mm) in 2015.
St. Louis experiences thunderstorms 48 days a year on average. Especially in the spring, these storms can often be severe, with high winds, large hail and tornadoes. Lying within the hotbed of Tornado Alley, St. Louis reigns as one of the most frequently tornadic metropolitan areas, and has an extensive history of particularly damaging tornadoes. Severe flooding, such as the Great Flood of 1993, may occur in spring and summer; the (often rapid) melting of thick snow cover upstream either the Missouri or Mississippi Rivers can contribute to springtime flooding.
As for averages, here is another quick breakdown. As per usual, all temperatures in Fahrenheit are not in parentheses, while those in Celsius are.
Average temperatures:
Average high temperatures in January is 39.9 (4.4) degrees, while average low temperatures are 23.7 (−4.6) degrees.
Average high temperatures in February is 45.0 (7.2) degrees, while average low temperatures are 27.6 (−2.4) degrees.
Average high temperatures in March is 55.9 (13.3) degrees, while average low temperatures are 36.6 (2.6) degrees.
Average high temperatures in April is 67.4 (19.7) degrees, while average low temperatures are 47.2 (8.4) degrees.
Average high temperatures in May is 76.3 (24.6) degrees, while average low temperatures are 57.2 (14) degrees.
Average high temperatures in June is 85.1 (29.5) degrees, while average low temperatures are 66.8 (19.3) degrees.
Average high temperatures in July is 89.1 (31.7) degrees, while average low temperatures are 71.0 (21.7) degrees.
Average high temperatures in August is 87.9 (31.1) degrees, while average low temperatures are 69.4 (20.8) degrees.
Average high temperatures in September is 80.2 (26.8), while average low temperatures are 60.6 (15.9) degrees.
Average high temperatures in October is 68.5 (20.3), while average low temperatures are 49.0 (9.4) degrees.
Average high temperatures in November is 55.5 (13.1) while average low temperatures are 38.1 (3.4) degrees.
Average high temperatures in December is 42.5 (5.8) while average low temperatures are 26.9 (−2.8) degrees.
Average high temperatures combined (all monthly temperatures combined and averaged) is 66.2 (19) while average low temperatures combined is 47.9 (8.8) degrees.