Climate of usa

CLIMATE OF USA
The Climate of the United States varies due to its positioning of states in latitude, and range of geographic features. West of the 100th meridian, much of the US is semi-arid to desert in the far southwestern US. To the east of the 100th meridian, the climate is humid continental in the northern areas (locations above 40 north latitude), to humid temperate in the central and Atlantic coast regions, to humid subtropical in the Gulf and south Atlantic regions. The southern tip of Florida is tropical. Much of the Rocky Mountains, the Sierra Nevada, and the Cascade Range are alpine. The climate along the coast of California is Mediterranean, while the upper West coast areas in coastal Oregon and Washington are cool temperate oceanic. The state of Alaska—on the northwestern corner of the North American continent—is largely subarctic, with an oceanic climate in its southern edge and a polar climate in the north. The archipelago state of Hawaii, in the middle of the Pacific Ocean, is tropical.Like most land masses located in the middle and lower middle latitudes, the primary driver of weather in the contiguous United States is the seasonal change in the solar angle, the migration north/south of the subtropical highs, and the seasonal change in the position of the polar jet stream. In the northern hemisphere summer, the oceanic subtropical high pressure systems move north[clarification needed] - and much of the central and southern US see stable weather, and warm to hot temperatures. In the Northern Hemisphere winter, the subtropical highs retreat southward and the polar front jet stream moves further south into the United States - bringing much greater weather variation and much colder temperature. Areas in the extreme southern US (Florida, the Gulf Coast, the Desert Southwest, and southern California) however, often have more stable weather as the polar jet stream’s impact does not usually reach that far south.
Mobile weather systems (cyclones/fronts/jets) are more active in the winter/colder months than in the summer/warmer months in the United States. In the winter months, storms come from the Pacific Ocean and enter the US through the Pacific Northwest, then move out across the Great Plains, then move eastward off the central and northern Atlantic seaboard. In the summer months, storms are much more localized (short duration thunderstorms are common in many areas east of the 100th meridian) and large scale storms are much less frequent and the duration is much shorter. In late summer and fall, tropical cyclones infrequently move toward the Gulf and south Atlantic states, bringing high winds, heavy rainfall, and tidal surges to the coastal plain.Extreme weather is not uncommon—tornadoes regularly occur in the area of the Midwest referred to as Tornado Alley, heavy snowstorms can impact the far northern areas, and tropical cyclones can strike the far southern areas. The United States has more tornadoes than the rest of the countries of the world combined.The Southwest is a hot desert climate, cities like Phoenix, Las Vegas, Yuma, and Palm Springs have average highs over 100 °F (38 °C) during the summer months. In winter, daily temperatures in the southwest are cooler with highs in the 60 °F (16 °C)’s and lows in the 30 °F (−1 °C) and 40 °F (4 °C)s. Rainfall in the southwest average less than 0.7 inches (18 mm) of rain monthly. The Southwest and the Great Basin are affected by the monsoon from the Gulf of California from July–September. This brings localized thunderstorms to the region that can result in flash flooding. Despite this, drought has been frequent in the region, often lasting for periods of years or longer. Forest Fires across the Western United States (especially the southwest) occur annually.[citation needed] The far southwest (California coast) has a Mediterranean climate. Like most Mediterranean climates, coastal California has a wet winter and dry summer. Early summers can often bring cooler and overcast weather (low stratus clouds) to coastal California. As such the warmest summer weather is delayed until August and September in many areas of the California coast. Upwelling of cold Pacific waters also contributes to the frequent chilly weather in coastal California, especially coastal areas in northern California. Daily high temperatures range from the mid and upper 70’s in the summer to the low to mid 60 °F (16 °C)’s in winter...with low temperatures from the 60 °F (16 °C)’s in summer to the 40 °F (4 °C)’s in winter.[citation needed] Southeast
The southeast has a warm to hot, humid, subtropical climate. Cities like Houston, New Orleans, Orlando, and Charleston have average highs in the lower 90 °F (32 °C)'s, and combined with the moist tropical air, creates sultry summer weather conditions. In winter, daily temperatures in the southeast reach highs in the 50 °F (10 °C)’s and 60 °F (16 °C)’s and lows from 35 °F (2 °C) to 50 F (10 C). Winter is also the dry season in parts of the far southern areas of the southeast (northern Florida, south Georgia). Rainfall is plentiful in the southeastern US, and summer is normally the wettest time, especially in areas along the Gulf and south Atlantic coast.[citation needed]Southern Florida has a tropical climate, with all months having a mean temperature of higher than 65 °F (18 °C). Like most tropical climates, southern Florida has a wet summer and dry and sunny winter. In cities like Fort Lauderdale, Miami, Naples, and Palm Beach average daily highs range from the upper 70 °F (21 °C)’s in winter to the upper 80 °F (27 °C)’s and low 90 °F (32 °C)’s in summer. Overnight lows range from the 70 °F (21 °C)’s in summer to the upper 50 °F (10 °C)’s and low 60 °F (16 °C)’s in winter. The only area of the US mainland known to have never experience a freeze (32 °F (0 °C)) is the Florida Keys and some areas of coastal south Florida.[citation needed] North-Central/Midwestern/New England
The Midwest, northern Plains, Great Lakes, and New England regions have a humid continental climate. Here there are four seasons with warm to hot summers, cold and snowy winters, and rain in all seasons. Temperatures can rise or drop rapidly; winds can be extreme; and the flow of dry or moist hot air from the subtropics clashing with incoming air from the subarctic can spawn tornadoes, particularly in the Spring and in the Midwest and Plains. In winter, snowstorms can bring heavy lake effect snows to the areas from Wisconsin, Michigan, Ohio, and New York, and northeasters can bring heavy snow/rain/and coastal flooding to the Boston/New England region. Temperatures can plunge to −20 °F (−29 °C) to −30 °F (−34 °C) in the winter at night in the northern areas of the region. In summer, temperatures surpass 90 °F (32 °C)s on the hotter days and can reach 100 °F (38 °C) for a short time.[citation needed]
Southern Plains/Atlantic Coast (NYC to North Carolina)
The central plains and East Coast (NYC/Connecticut southward) has a temperate humid climate. Cities in this region like St. Louis, Cincinnati, and NYC, have hot summers that are humid and moderately cold to cool winters with occasional snowfall, sometimes heavy. Rainfall is spread fairly evenly throughout the year, though there is a reversal of wind between summer and winter along the East Coast.
Most areas from NYC south to North Carolina have more rainfall in the six warmer months (May through October) when the winds are often from a southerly direction (onshore), than in the six cooler months (November through April), when winds are often from a northerly direction and offshore.[citation needed]
Pacific Northwest
The Pacific Northwest has a temperate oceanic climate. The climate is wet and cool in fall, winter, and early spring, stable and drier in the summer months. In winter rain, upwards of 100 inches (2,500 mm) annually[clarification needed] in some areas, create an overcast and cool climate, but without severe cold like the interior northern US. Cool summers along the immediate coastline are also common. The Great Basin and Columbia Plateau (the Intermontane Plateaus) are arid or semiarid regions with high summer temperatures surpassing 100 °F (38 °C)'s at low elevations, with annual precipitation averages less than 15 inches (380 mm) as a result of the rain shadow of the Sierra Nevada and Cascades.[citation needed]