In general, the climate of Quebec is cold and humid. The climate of the province is largely determined by its latitude, maritime and elevation influences. According to the Köppen climate classification, Quebec has three main climate regions. Southern and western Quebec, including most of the major population centres and areas south of 51oN, have a humid continental climate (Köppen climate classification "Dfb") with four distinct seasons having warm to occasionally hot and humid summers and often very cold and snowy winters. The main climatic influences are from western and northern Canada and move eastward, and from the southern and central United States that move northward. Because of the influence of both storm systems from the core of North America and the Atlantic Ocean, precipitation is abundant throughout the year, with most areas receiving more than of precipitation, including over of snow in many areas. During the summer, severe weather patterns (such as tornadoes and severe thunderstorms) occur occasionally. Most of central Quebec, ranging from 51 to 58 degrees North has a subarctic climate (Köppen "Dfc"). Winters are long, very cold, and snowy, and among the coldest in eastern Canada, while summers are warm but very short due to the higher latitude and the greater influence of Arctic air masses. Precipitation is also somewhat less than farther south, except at some of the higher elevations. The northern regions of Quebec have an arctic climate (Köppen "ET"), with very cold winters and short, much cooler summers. The primary influences in this region are the Arctic Ocean currents (such as the Labrador Current) and continental air masses from the High Arctic.