The urban area of St. Louis has a damp subtropical climate; however, its metropolitan region even to the south may present a hot-summer humid continental climate, which shows the effect of the urban heat island in the city. Without the presence of water bodies its winters may be colder than Boston, but its summers may be more similar to those of Lubbock, Texas than other areas to the east. 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 is one of the most frequently tornadic metropolitan areas in the U.S. 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 on the Missouri or Mississippi Rivers can contribute to springtime flooding.
