What causes a humid subtropical climate?

Humid, subtropical climates occur where four factors intersect: latitude between 20 and 40 degrees north or south, onshore movement of humid air masses in summer and cyclonic storms in winter. Humid, subtropical climates are usually on a continent's southeastern coast but may extend well inland.

Humid, subtropical climates have long, hot, humid summers and mild winters. The Trewartha climate classification defines this climate as having at least eight months of mean temperatures above 50 degrees Fahrenheit annually. Rainfall in humid, subtropical climates often shows a summer peak. Most of the American Southeast has this type of climate, and this climate is found on all continents except Antarctica.