The United States of America covers a large region, stretching from east to west across nine time zones. Therefore, it is no surprise that the country has a varied climate, ranging from arctic regions to deserts. California, on the west coast of the US, has a pleasant, Mediterranean climate, and the Pacific Northwest Coast has more of a maritime climate, with cooler summers and mild winters, influenced by westerly winds. The central part of the US has extreme temperature variations and a continental climate - with cold winters and hot summers. The eastern central US tends to be more humid, while the western central US is semiarid. The east side of the country has a continental climate caused by air masses moving from west to east, with hot summers and a prevalence of tornadoes in the Mississippi River area. Florida has the warmest winters on the eastern seaboard. It is recommended that travellers research the climate in the specific state they wish to visit when choosing when to travel.