The Climate of the USA!
• The climate of the United States varies due to differences in latitude, and a range of geographic features, including mountains and deserts. West of the 100 th meridian, much of the US is semiarid to arid, even desert in the far southwestern US. East of the 100 th meridian, the climate is humid continental in the northern areas (locations above 40 north latitude), to humid temperate in the central and middle Atlantic coast regions, to humid subtropical climate in the Gulf and south Atlantic regions.
• The Great Plains, the Midwest and the southern United States - because of contrasting air masses - have frequent severe thunderstorms and tornado outbreaks during spring and summer. In central portions of the US, tornadoes are more common than anywhere else on Earth and touch down most commonly in the spring and summer. The strip of land from north Texas north to Nebraska and east into Southern Michigan is known as Tornado Alley, where many houses have tornado shelters and many towns have tornado sirens.
• The Appalachian region and the Midwest experience the worst floods. Widespread severe flooding is rare. Localized flooding can, however, occur anywhere, and mudslides from heavy rain cause problems in any mountainous area, particularly the Southwest. The narrow canyons of many mountain areas in the west and severe thunderstorm activity during the monsoon season in summer leads to sometimes devastating flash floods. • In 2013, the US sustains $10 billion annually in damage from floods. • The Southwest has the worst droughts; one is thought to have lasted over 500 years and to have decimated the Anasazi people. Large stretches of desert shrub in the west can fuel the spread of wildfires.
In the Northern Hemisphere summer, the "Bermuda High" over the subtropical Atlantic Ocean typically sends warm, humid air over the eastern, southern and central United States - resulting in southerly airflow, warm to hot temperatures, high humidity and occasional thunderstorm activity. In summer, high pressure over the north-central Pacific typically results in northwesterly airflow, stable conditions and cool to mild conditions along most of the immediate Pacific coast, from Washington state to San Diego, CA.
