Climate
The Köppen classification depends on average monthly values of temperature and precipitation. The most commonly used form of the Köppen classification has five primary types labeled A through E. These primary types are A) tropical, B) dry, C) mild mid-latitude, D) cold mid-latitude, and E) polar. The five primary classifications can be further divided into secondary classifications such as rainforest, monsoon, tropical savanna, humid subtropical, humid continental, oceanic climate, Mediterranean climate, desert, steppe, subarctic climate, tundra, and polar ice cap.
Climate of Minneapolis–Saint Paul
The Twin Cities experiences a wide range of precipitation types. Rain is the most common form during the summer months, while snow, sleet, freezing rain, and occasionally rain occur during the winter. The summer months of June, July and August account for nearly half of the annual precipitation total across the Twin Cities. Most of this rain falls from thunderstorms, a frequent summer occurrence. Even though summer is the primary season for the Twin Cities to experience thunderstorms, they can occur from March to November. On rare occasions thundersnow can occur, where thunder and lightning accompanies winter or (more usually) spring snowstorms. During spring and summer, some thunderstorms are severe. These storms produce damaging straight line winds, large hail and, occasionally, a tornado. The Twin Cities has experienced several major derecho events, most recently during the Late-May 1998 Tornado Outbreak and Derecho which traveled from South Dakota to New York on May 30 – May 31, 1998. Summertime thunderstorms are fueled by dew points that often reach into the 70s °F (21 °C) and sometimes even .