A monsoon is a seasonal change in the direction of the prevailing, or strongest, winds of a region. Monsoons cause wet and dry seasons throughout much of the tropics. Monsoons are most often associated with the Indian Ocean.

Monsoons always blow from cold to warm regions. The summer monsoon and the winter monsoon determine the climate for most of India and Southeast Asia.

Summer Monsoon

The summer monsoon is associated with heavy rainfall. It usually happens between April and September. As winter ends, warm, moist air from the southwest Indian Ocean blows toward countries like India, Sri Lanka, Bangladesh, and Myanmar. The summer monsoon brings a humid climate and torrential rainfall to these areas.

India and Southeast Asia depend on the summer monsoon. Agriculture, for example, relies on the yearly rain. Many areas in these countries do not have large irrigation systems surrounding lakes, rivers, or snowmelt areas. Aquifers, or supplies of underground water, are shallow. The summer monsoon fills wells and aquifers for the rest of the year. Rice and tea are some crops that rely on the summer monsoon. Dairy farms, which help make India the largest milk producer in the world, also depend on the monsoon rains to keep cows healthy and well-fed.

Industry in India and Southeast Asia also relies on the summer monsoon. A great deal of electricity in the region is produced by hydroelectric power plants, which are driven by water collected during the monsoons. Electricity powers hospitals, schools, and businesses that help the economies of these areas develop.

When the summer monsoon is late or weak, the regions economy suffers. Fewer people can grow their own food, and large agribusinesses do not have produce to sell. Governments must import food. Electricity becomes more expensive, sometimes limiting development to large businesses and wealthy individuals. The summer monsoon has been called Indias true finance minister.

Heavy summer monsoons can cause great damage. Residents of such urban areas as Mumbai, India, are used to the streets flooding with almost half a meter (1.5 feet) of water every summer. However, when the summer monsoon is stronger than expected, floods can devastate the region. In cities like Mumbai, entire neighborhoods can be drowned. In rural areas, mudslides can bury villages and destroy crops.

In 2005, a strong monsoon devastated western India. As the summer monsoon blew in from the southwest, it first hit the state of Gujarat. More than 100 people died. Then, the monsoon rains hit the state of Maharashtra. Flooding in Maharashtra killed more than 1,000 people. On July 26, 2005, the city of Mumbai, Maharashtra, received almost a meter (39.1 inches) of rain.

Winter Monsoon

The Indian Oceans winter monsoon, which lasts from October to April, is less well-known than its rainy summer equivalent. The dry winter monsoon blows from the northeast. These winds start in the air above Mongolia and northwestern China.

Winter monsoons are less powerful than summer monsoons in Southeast Asia, in part because the Himalaya Mountains prevent much of the wind and moisture of the monsoons from reaching the coast. The Himalayas also prevent much of the cool air from reaching places like southern India and Sri Lanka, keeping them warm all year. Winter monsoons are sometimes associated with droughts.

Not all winter monsoons are dry, however. Unlike the western part of Southeast Asia, the eastern, Pacific coast of Southeast Asia experiences its rainy season in the winter. The winter monsoon brings moist air from the South China Sea to areas like Indonesia and Malaysia.

Other Monsoons

The Asian-Australian monsoon, which includes the Indian Ocean, stretches from northern Australia to Russias Pacific coast. This huge monsoon wind system then stretches into the Indian Ocean. Finally, it reaches its end on the Indian coast of Africa.

Monsoon winds exist in other parts of the world, too. The North American monsoon happens once a year, usually in the middle of summer. Warm, moist air from the Gulf of California blows northeast, while warm, moist air from the Gulf of Mexico blows northwest. These two winds meet over the Sierra Madre Occidental mountains in central Mexico. The monsoon brings moisture to the mountain ecosystem before continuing north to the U.S. states of Arizona, New Mexico, and Texas.

The North American monsoon can be a natural aid to firefighters. Summer temperatures in Arizona regularly reach more than 100 degrees Fahrenheit, making wildfires difficult to contain. The North American monsoon is also the primary water source for most desert ecosystems in the region. However, it can also confuse and interrupt daily life for people and businesses not used to dealing with heavy rain.

monsoon
The rice paddies of Southeast Asia depend on the seasonal monsoon.

Monsoon Cup
The Monsoon Cup is an international yachting race held every year in the state of Terengganu, Malaysia. The race is held during monsoon season, making it a challenging race for sailors.

Monsoon Zone
The Monsoon Zone is a belt of low-pressure air currents that circle the Earth at the Equator. The Monsoon Zone is also known as the Intertropical Convergence Zone (ITCZ). The Monsoon Zone is usually warm and experiences mild winds.

At sea, the Monsoon Zone is known as the Doldrums due to its lack of winds.

agribusiness
Noun

the strategy of applying profit-making practices to the operation of farms and ranches.

Noun

the art and science of cultivating the land for growing crops (farming) or raising livestock (ranching).

aid
Noun

help or assistance.

Noun

an underground layer of rock or earth which holds groundwater.

Asian-Australian monsoon
Noun

weather system stretching from Australia to Africa, bringing rainy seasons and dry seasons to most of Southeast Asia.

Noun

all weather conditions for a given location over a period of time.

contain
Verb

to keep under control, hold, or prevent escape.

cow
Noun

large, domesticated mammal used for milk and meat.

Noun

agricultural produce.

Noun

steady, predictable flow of fluid within a larger body of that fluid.

dairy
Adjective

having to do with the production of milk, cream, butter, or cheese.

damage
Noun

harm that reduces usefulness or value.

Noun

area of land that receives no more than 25 centimeters (10 inches) of precipitation a year.

devastate
Verb

to destroy.

doldrums
Noun

areas of calm winds north of the Equator in the Pacific, Atlantic, and Indian Oceans.

Noun

period of greatly reduced precipitation.

drown
Verb

to die or suffocate in a liquid.

dry
Adjective

arid or lacking in moisture.

economy
Noun

system of production, distribution, and consumption of goods and services.

Noun

community and interactions of living and nonliving things in an area.

electricity
Noun

set of physical phenomena associated with the presence and flow of electric charge.

Noun

imaginary line around the Earth, another planet, or star running east-west, 0 degrees latitude.

finance minister
Noun

person responsible for a nation's economy.

firefighter
Noun

person who works to control and put out fires.

Noun

overflow of a body of water onto land.

humid
Adjective

air containing a large amount of water vapor.

hydroelectric power
Noun

usable energy generated by moving water converted to electricity.

import
Verb

to bring in a good or service from another area for trade.

industry
Noun

activity that produces goods and services.

Intertropical Convergence Zone (ITCZ)
Noun

belt of low-pressure air currents that circle the Earth at the Equator. Also known as the Monsoon Zone.

Noun

watering land, usually for agriculture, by artificial means.

moisture
Noun

wetness.

Noun

seasonal change in the direction of the prevailing winds of a region. Monsoon usually refers to the winds of the Indian Ocean and South Asia, which often bring heavy rains.

Monsoon Cup
Noun

yachting competition held in Malaysia during the winter.

Monsoon Zone
Noun

belt of low-pressure air currents that circle the Earth at the Equator. Also known as the Intertropical Convergence Zone (ITCZ).

mountain
Noun

landmass that forms as tectonic plates interact with each other.

mudslide
Noun

rapid, downhill flow of soil and water. Also called a mudflow.

Noun

an area within a larger city or town where people live and interact with one another.

North American monsoon
Noun

summer weather system bringing the rainy season to central Mexico and the Southwest United States.

prevailing wind
Noun

wind that blows from one direction.

primary
Adjective

first or most important.

rainfall
Noun

amount of precipitation that falls in a specific area during a specific time.

rainy season
Noun

time of year when most of the rain in a region falls.

rice
Noun

grass cultivated for its seeds.

Noun

period of the year distinguished by special climatic conditions.

summer monsoon
Noun

change in the direction of a prevailing wind, resulting in a region's rainy season or dry season.

tea
Noun

plant native to Asia cultivated for its leaves.

torrential
Adjective

heavy, fast-flowing.

Plural Noun

region generally located between the Tropic of Cancer (23 1/2 degrees north of the Equator) and the Tropic of Capricorn (23 1/2 degrees south of the Equator).

Noun

developed, densely populated area where most inhabitants have nonagricultural jobs.

wealthy
Adjective

very rich.

well
Noun

a hole drilled in the Earth to obtain a liquid or gaseous substance.

Noun

uncontrolled fire that happens in a rural or sparsely populated area.

wind
Noun

movement of air (from a high pressure zone to a low pressure zone) caused by the uneven heating of the Earth by the sun.

winter monsoon
Noun

change in the direction of a prevailing wind, resulting in a region's rainy season or dry season.

yachting
Noun

sport of racing large sailing vessels.