World | North America |
Scientists define a desert as a region that receives less than 25 centimeters (10 inches) of rain per year. About one-third of Earth's land surface is desert. Deserts may be hot or cold, with great expanses of barren sand or snow or sandy gravel with hardy vegetation. In hot deserts precipitation falls as rain; in cold deserts, it falls as snow. Both types of desert have there is very little precipitation and very low humidity.
The hot arid climate zone in the
western United States has predictably
warm, dry winters and very hot, dry
summers. Arizona and parts of Nevada,
Utah, and California are sunny and
dry all year. Little rain falls during
most of the year. During the summer
the temperature can be very high, and
thunderstorms can deliver heavy rains
that can cause flash floods. The hot
arid zone supports a wide diversity
of drought-resistant plants, including
cactus, mesquite, and yucca, and a host
of burrowing and sun-loving animals.
The interior continental semiarid zone
is characterized by warm spring and
summer weather, cold winters, and
summer thunderstorms with the
possibility of tornadoes. The semiarid
climate supports large expanses of
sagebrush and huge grasslands. Land
in the interior continental semiarid
zone is often used by ranchers to
graze livestock.
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Two climate zones occur in
Alaska. They are the subarctic
and the arctic. The climate is
extremely cold most of the year,
with variable precipitation.
The high-altitude zone
found high in the mountains
supports large forests of
evergreen trees and provides
the right conditions for skiing
and other winter sports
requiring snow.
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The humid midaltitude climate zone includes the midwestern United States, New England, and the southern part of Canada. This climate zone supports huge diverse forests of deciduous and evergreen trees and all the animals that forests support.
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Hawaii has a tropical wet and
dry climate, warm and sunny all
year long with plenty of tropical
rain in many parts of the islands.
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Weather in the dry
subtropical zone is usually
warm and rainy in the
winter but hot and dry in the
summer. The dry subtropical
zone supports oak woodlands,
chaparral, and a very diverse
community of brush,
grasses, and mixed forests.
Dry subtropical climates are
excellent for farming, fruit
orchards, vegetable gardens,
and raising livestock.
The weather in the southeastern
United States is significantly different.
Florida, Mississippi, Louisiana, and
North Carolina rarely have snow in
the winter, and the summers and
springs are rainy, hot, and humid. The
southern states fall into the humid
subtropical climate zone. This zone
supports large hardwood forests and
many kind of vines.
The temperate marine zone of
the Pacific Northwest is cool and
wet throughout the year. The
climate is strongly influenced by
the Pacific Ocean, which keeps
the weather cool and moist. This
climate zone is characterized by
dense forests of large evergreen
trees: redwood, fir, pine, and
spruce. The moist forests are often
home to ferns, mosses, lichens,
and fungi. Winters are cool and
rainy, while summers are cool and
can be foggy and wet.
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