page_title: Wet season
section_title: Effects
hierarchical_section_title: Wet season / Effects
context_page_description: The wet 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 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.
context_section_description: 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.
caption: Monsoon in the Vindhya mountain range, central India.
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