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Wet season

earth science Maturity 5-7 Next article →

A wet season is a specific period during the year when a region receives most of its annual precipitation.

Cairns climate
Cairns climate

This duration typically lasts for at least one month. While many people call it the rainy season, it is sometimes referred to as the monsoon season. In some tourist areas, the term "green season" is used as a euphemism. The timing and intensity of these seasons vary depending on the local climate. For example, tropical rainforests do not have wet seasons because their rainfall is distributed evenly throughout the year.

MeanMonthlyP
MeanMonthlyP

In contrast, tropical seasonal forests experience distinct dry and wet periods.

In many tropical and subtropical regions, the mechanism of rainfall is driven by daytime heating. As the sun heats the ground, it warms the air within a moist airmass. This process triggers diurnal thunderstorm activity, which refers to storms that occur every day. These thunderstorms often develop in the late afternoon or early evening. Interestingly, much of the total daily rainfall occurs in the very first minutes of a downpour. This happens before the storms mature into a stratiform stage, which is a period of more steady, widespread rain.

Darwin thunderstorm
Darwin thunderstorm

In some areas, a wind shift accompanies the heavy rain, which is a defining characteristic of a monsoon.

Different climate regimes determine when and how these seasons occur. Under the Köppen climate classification, a wet season month in a tropical climate is defined by a specific amount of average precipitation. Mediterranean climates follow a different pattern, featuring wet winters and dry summers. In the tropics, some regions may experience two wet seasons per year. This happens because the Intertropical Convergence Zone, or monsoon trough, can pass over a location twice. For instance, northern Guyana experiences one wet season in early spring and another in early winter. The Sonoran Desert is unique because it receives two different rainy seasons from both Mediterranean and monsoon climate regimes.

Geography plays a major role in where these seasons are found. Many savanna climates in Sub-Saharan Africa, such as Ghana, Burkina Faso, Ethiopia, and Botswana, have distinct rainy seasons. In the United States, subtropical areas like Florida, southern Louisiana, and parts of Texas experience them. Monsoon regions are vast, including the Indian subcontinent, Southeast Asia, and northern Australia. Even the Mediterranean coastline, including Italy, Greece, and Turkey, has a wet season during the winter months. The Negev Desert in Israel also sees its wet season extend from October through May.

These seasonal shifts have significant impacts on the environment and human life. The heavy rainfall can improve air quality and the quality of fresh water. It also helps to charge local aquifers, which are underground layers of water-bearing rock. This can lead to more balanced pH levels in the water. Vegetation grows substantially during these times, which can lead to higher crop yields later in the season. Successful crops planted during this time include maize, rice, millet, cassava, groundnut, and yam. However, the previous dry season often causes food shortages because crops have not yet reached maturity.

Despite the benefits, the wet season can bring serious challenges. Heavy rainfall can cause rivers to overflow their banks, leading to widespread flooding. In mountainous areas, this can result in dangerous landslides and mudflows. Flooding can be made worse if fires occurred during the previous dry season. Such fires can make sandy or loamy soils hydrophobic, meaning they become water-repellent. This causes water to run off the surface rather than soaking in. Additionally, heavy runoff can increase soil erosion and deplete essential nutrients through a process called leaching.

During the rainy season Chattogram,Bangladesh
During the rainy season Chattogram,Bangladesh

Biological and social systems must adapt to these changes. In tropical areas, the wet season can increase the incidence of diseases like malaria and dengue, especially when it coincides with high temperatures. Animals often develop specific survival strategies or retreat to higher ground to avoid rising waters.

East - Guinean Savanna 001
East - Guinean Savanna 001

For humans in developing countries, the wet season can cause seasonal weight changes. People may experience a drop in weight during the rains until the first harvest allows their weight to rebound. To manage these risks, governments use tools like flood plain mapping to identify high-risk areas and provide instructions on controlling erosion.

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🖼️ Images & Media (6)
File:Cairns climate.svg
Cairns climate.svg
File:Darwin thunderstorm.jpg
Darwin thunderstorm.jpg
File:During the rainy season Chattogram,Bangladesh.jpg
During the rainy season Chattogram,Bangladesh.jpg
File:MeanMonthlyP.gif
MeanMonthlyP.gif
File:EatonCanyonWetSeason.jpg
EatonCanyonWetSeason.jpg
File:East - Guinean Savanna 001.jpg
East - Guinean Savanna 001.jpg
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