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The wet season (sometimes called the rainy season or monsoon season) is the time of year when most of a region's average annual rainfall occurs.  Generally, the season lasts at least a month.  The term green season is also sometimes used as a euphemism by tourist authorities.  Areas with wet seasons are dispersed across portions of the tropics and subtropics. 
Under the Köppen climate classification, for tropical climates, a wet season month is defined as a month where average precipitation is 60 millimetres (2.4 in) or more.  In contrast to areas with savanna climates and monsoon regimes, Mediterranean climates have wet winters and dry summers. Dry and rainy months are characteristic of tropical seasonal forests: in contrast to tropical rainforests, which do not have dry or wet seasons, since their rainfall is equally distributed throughout the year.  Some areas with pronounced rainy seasons will see a break in rainfall mid-season, when the intertropical convergence zone or monsoon trough moves to higher latitudes in the middle of the warm season. 
When the wet season occurs during a warm season, or summer, precipitation falls mainly during the late afternoon and early evening. In the wet season, air quality improves, fresh water quality improves, and vegetation grows substantially, leading to crop yields late in the season. Rivers overflow their banks, and some animals retreat to higher ground. Soil nutrients diminish and erosion increases. The incidence of malaria and dengue increases in areas where the rainy season coincides with high temperatures, particularly in tropical areas.  Some animals have adaptation and survival strategies for the wet season. Often, the previous dry season leads to food shortages in the wet season, as the crops have yet to mature. Crops which can be successfully planted during the wet or rainy season are cassava, maize, groundnut, millet, rice and yam.  The temperate counterpart to the tropical wet season is spring or autumn.
In areas where the heavy rainfall is associated with a wind shift, the wet season is known as the monsoon season. Many tropical and subtropical climates experience monsoon rainfall patterns.  Rainfall in the wet season is mainly due to daytime heating, which leads to diurnal thunderstorm activity within a pre-existing moist airmass , so the rain mainly falls in late afternoon and early evening in savannah and monsoon regions.
Much of the total rainfall each day occurs in the first minutes of the downpour,  before the storms mature into their stratiform stage.  Most places have only one wet season, but areas of the tropics can have two wet seasons, because the monsoon trough, or Intertropical Convergence Zone, can pass over locations in the tropics twice per year. However, since rain forests have rainfall spread evenly through the year, they do not have a wet season. 
Areas with a savanna climate in Sub-Saharan Africa, such as Ghana, Burkina Faso,   Darfur,  Eritrea,  Ethiopia,  and Botswana have a distinct rainy season.  Also subtropical areas like Florida, South and Southeast Texas, and southern Louisiana have a rainy season.  Monsoon regions include the Indian subcontinent, Southeast Asia (including Indonesia and Philippines),  northern sections of Australia,  Polynesia,  Central America,  western and southern Mexico,  the Desert Southwest of the United States,  southern Guyana,  and northeast Brazil. 
Northern Guyana has two wet seasons: one in early spring and the other in early winter.  In western Africa, there are two rainy seasons across southern sections, but only one across the north.  Within the Mediterranean climate regime, the west coast of the United States, the southwest coast of Australia and South Africa, the Mediterranean coastline of Italy, Spain, Greece,  Lebanon, Syria, Algeria, Morocco, Tunisia, and Turkey, as well as areas further inland in Western Asia which include Jordan, Northern Iraq and most parts of Iran, experience a wet season in the winter months.  Similarly, the wet season in the Negev desert of Israel extends from October through May.  At the boundary between the Mediterranean and monsoon climates lies the Sonoran desert, which receives the two rainy seasons associated with each climate regime. 
The wet season is known by many different local names throughout the world. For example, in Mexico it is known as "storm season". Different names are given to the various short "seasons" of the year by the First Nations of Northern Australia: the wet season typically experienced there from December to March is called Gudjewg. The precise meaning of the word is disputed, although it is widely accepted to relate to the severe thunderstorms, flooding, and abundant vegetation growth commonly experienced at this time. 
In tropical areas, when the monsoon arrives, high daytime high temperatures drop and overnight low temperatures increase, thus reducing diurnal temperature variation.  During the wet season, a combination of heavy rainfall and, in some places such as Hong Kong, an onshore wind, improve air quality. 
In Brazil, the wet season is correlated with weaker trade winds off the ocean.  The pH level of water becomes more balanced due to the charging of local aquifers during the wet season.  Water also softens, as the concentration of dissolved materials reduces during the rainy season.  Erosion is also increased during rainy periods. 
Arroyos that are dry at other times of the year fill with runoff, in some cases with water as deep as 10 feet (3.0 m).  Leaching of soils during periods of heavy rainfall depletes nutrients.  The higher runoff from land masses affects nearby ocean areas, which are more stratified, or less mixed, due to stronger surface currents forced by the heavy rainfall runoff. 
High rainfall can cause widespread flooding,  which can lead to landslides and mudflows in mountainous areas.  Such floods cause rivers to burst their banks and submerge homes.  The Ghaggar-Hakra River, which only flows during India's monsoon season, can flood and severely damage local crops.  Floods can be exacerbated by fires that occurred during the previous dry season, which cause soils which are sandy or composed of loam to become hydrophobic, or water repellent.  In various ways governments may help people deal with wet season floods. Flood plain mapping identifies which areas are more prone to flooding.  Instructions on controlling erosion through outreach[ clarification needed ] are also provided by telephone or the internet. 
The wet season is the main period of vegetation growth within the Savanna climate regime.  However, this also means that wet season is a time for food shortages before crops reach their full maturity.  This causes seasonal weight changes for people in developing countries, with a drop occurring during the wet season until the time of the first harvest, when weights rebound.  Malaria incidence increases during periods of high temperature and heavy rainfall. 
Cows calve, or give birth, at the beginning of the wet season.  The onset of the rainy season signals the departure of the monarch butterfly from Mexico.  Tropical species of butterflies show larger dot markings on their wings to fend off possible predators and are more active during the wet season than the dry season.  Within the tropics and warmer areas of the subtropics, decreased salinity of near shore wetlands due to the rains causes an increase in crocodile nesting.  Other species, such as the arroyo toad, spawn within the couple of months after the seasonal rains.  Armadillos and rattlesnakes seek higher ground. 
A monsoon is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with annual latitudinal oscillation of the Intertropical Convergence Zone (ITCZ) between its limits to the north and south of the equator. Usually, the term monsoon is used to refer to the rainy phase of a seasonally changing pattern, although technically there is also a dry phase. The term is also sometimes used to describe locally heavy but short-term rains.
The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at 23°26′10.6″ (or 23.43627°) N and the Tropic of Capricorn in the Southern Hemisphere at 23°26′10.6″ (or 23.43627°) S. The tropics are also referred to as the tropical zone and the torrid zone.
In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls from clouds due to gravitational pull. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. Precipitation occurs when a portion of the atmosphere becomes saturated with water vapor, so that the water condenses and "precipitates" or falls. Thus, fog and mist are not precipitation but colloids, because the water vapor does not condense sufficiently to precipitate. Two processes, possibly acting together, can lead to air becoming saturated: cooling the air or adding water vapor to the air. Precipitation forms as smaller droplets coalesce via collision with other rain drops or ice crystals within a cloud. Short, intense periods of rain in scattered locations are called showers.
The subtropical zones or subtropics are geographical and climate zones to the north and south of the tropics. Geographically part of the temperate zones of both hemispheres, they cover the middle latitudes from 23°26′10.6″ (or 23.43627°) to approximately 35° north and south. The horse latitudes lie within this range.
Tropical climate is the first of the five major climate groups in the Köppen climate classification identified with the letter A. Tropical climates are defined by a monthly average temperature of 18 °C (64.4 °F) or higher in the coolest month, and feature hot temperatures all year-round. Annual precipitation is often abundant in tropical climates, and shows a seasonal rhythm but may have seasonal dryness to varying degrees. There are normally only two seasons in tropical climates, a wet season and a dry season. The annual temperature range in tropical climates is normally very small. Sunlight is intense in these climates.
The climate of India consists of a wide range of weather conditions across a vast geographic scale and varied topography. Based on the Köppen system, India hosts six major climatic sub types, ranging from arid deserts in the west, alpine tundra and glaciers in the north, and humid tropical regions supporting rain forests in the southwest and the island territories. Many regions have starkly different microclimates, making it one of the most climatically diverse countries in the world. The country's meteorological department follows the international standard of four seasons with some local adjustments: winter, summer, monsoon (rainy) season, and a post-monsoon period.
The monsoon trough is a portion of the Intertropical Convergence Zone in the Western Pacific, as depicted by a line on a weather map showing the locations of minimum sea level pressure, and as such, is a convergence zone between the wind patterns of the southern and northern hemispheres.
The characteristics of United States rainfall climatology differ significantly across the United States and those under United States sovereignty. Late summer and fall tropical cyclones bring precipitation which falls across the Gulf and Atlantic states. During the winter, and spring, Pacific storm systems bring Hawaii and the western United States most of their precipitation. Low pressure systems moving up the East coast bring cold season precipitation to the Mid-West and Northeast states, as well as Great Salt Lake and the Finger Lakes region. The snow to liquid ratio across the contiguous United States averages 13:1, meaning 13 inches (330 mm) of snow melts down to 1 inch (25 mm) of water.
Climate classifications are systems that categorize the world's climates. A climate classification may correlate closely with a biome classification, as climate is a major influence on life in a region. One of the most used is the Köppen climate classification scheme first developed in 1884.
Severe weather is any dangerous meteorological phenomenon with the potential to cause damage, serious social disruption, or loss of human life. Types of severe weather phenomena vary, depending on the latitude, altitude, topography, and atmospheric conditions. High winds, hail, excessive precipitation, and wildfires are forms and effects of severe weather, as are thunderstorms, downbursts, tornadoes, waterspouts, tropical cyclones, and extratropical cyclones. Regional and seasonal severe weather phenomena include blizzards (snowstorms), ice storms, and duststorms. Extreme weather phenomena that cause extreme heat, cold, wetness or drought often will bring severe weather events. One of the principal effects of anthropogenic climate change is changes in severe and extreme weather patterns.
Tropical savanna climate or tropical wet and dry climate is a tropical climate sub-type that corresponds to the Köppen climate classification categories Aw and As. The driest month has less than 60 mm (2.4 in) of precipitation and also less than mm of precipitation.
The climate of the United States varies due to changes in latitude, and a range of geographic features, including mountains and deserts. Generally, on the mainland, the climate of the U.S. becomes warmer the further south one travels, and drier the further west, until one reaches the West Coast.
The North American monsoon, variously known as the Southwest monsoon, the Mexican monsoon, the New Mexican monsoon, or the Arizona monsoon is a pattern of pronounced increase in thunderstorms and rainfall over large areas of the southwestern United States and northwestern Mexico, typically occurring between June and mid-September. During the monsoon, thunderstorms are fueled by daytime heating and build up during the late afternoon and early evening. Typically, these storms dissipate by late night, and the next day starts out fair, with the cycle repeating daily. The monsoon typically loses its energy by mid-September when much drier conditions are reestablished over the region. Geographically, the North American monsoon precipitation region is centered over the Sierra Madre Occidental in the Mexican states of Sinaloa, Durango, Sonora and Chihuahua.
Vietnam has a monsoon-influenced climate typical of that of mainland Southeast Asia. The diverse topography, long latitude, and influences from the South China Sea lead to climatic conditions varying significantly between regions. Northern Vietnam has a humid subtropical climate with the Köppen climate classification and has times to be influenced by cold waves from the Northeast, northern part of Central Vietnam also has times to be influenced by cold waves, southern part of Central Vietnam and Southern Vietnam are hot around year.
Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water for hydroelectric power plants, crop irrigation, and suitable conditions for many types of ecosystems.
An area of tropical monsoon climate is a tropical climate sub-type that corresponds to the Köppen climate classification category Am. Tropical monsoon climates have monthly mean temperatures above 18 °C (64 °F) in every month of the year and a dry season. The tropical monsoon climate is the intermediate climate between the wet Af and the drier Aw.
Earth rainfall climatology Is the study of rainfall, a sub-field of meteorology. Formally, a wider study includes water falling as ice crystals, i.e. hail, sleet, snow. The aim of rainfall climatology is to measure, understand and predict rain distribution across different regions of planet Earth, a factor of air pressure, humidity, topography, cloud type and raindrop size, via direct measurement and remote sensing data acquisition. Current technologies accurately predict rainfall 3–4 days in advance using numerical weather prediction. Geostationary orbiting satellites gather IR and visual wavelength data to measure realtime localised rainfall by estimating cloud albedo, water content, and the corresponding probability of rain.
The climate of Asia is dry across its southwestern region, with dry across much of the interior. Some of the largest daily temperature ranges on Earth occur in the western part of Asia. The monsoon circulation dominates across the southern and eastern regions, due to the Himalayas forcing the formation of a thermal low which draws in moisture during the summer. The southwestern region of the continent experiences low relief as a result of the subtropical high pressure belt; they are hot in summer, warm to cool in winter, and may snow at higher altitudes. Siberia is one of the coldest places in the Northern Hemisphere, and can act as a source of arctic air mass for North America. The most active place on Earth for tropical cyclone activity lies northeast of the Philippines and south of Japan, and the phase of the El Nino-Southern Oscillation modulates where in Asia landfall is more likely to occur. Many parts of Asia are being impacted by climate change.
The Monsoon of South Asia is among several geographically distributed global monsoons. It affects the Indian subcontinent, where it is one of the oldest and most anticipated weather phenomena and an economically important pattern every year from June through September, but it is only partly understood and notoriously difficult to predict. Several theories have been proposed to explain the origin, process, strength, variability, distribution, and general vagaries of the monsoon, but understanding and predictability are still evolving.
The Climate of Nigeria is mostly tropical. The nation, Nigeria has four climate types, two seasons and an average temperature, ranging between 24 °C and 30 °C. 2019 has been recorded as the country's wettest year and 1983 as the driest according to data from the Nigerian Meteorological Agency (NIMET).