The United States, with its large size and geographical variety, includes most climate types. To the east of the 100th meridian, the climate ranges from humid continental in the north to humid subtropical in the south. The southern tip of Florida is tropical, as is Hawaii. The Great Plains west of the 100th meridian are semi-dry. Much of the Western mountains are alpine. The climate is dry in the Great Basin, desert in the Southwest, Mediterranean in coastal California, and oceanic in coastal Oregon and Washington and southern Alaska. Most of Alaska is subarctic or polar. Extreme weather is not unusual—the states bordering the Gulf of Mexico are prone to hurricanes, and most of the world's tornadoes happen within the country, mainly in the Midwest's Tornado Alley.