Monsoon and rainy season

In short: The monsoon is a large-scale wind system that changes direction over the course of the year. In many tropical and subtropical regions it brings a distinct rainy season and a dry season.

In more detail: The name comes from the Arabic word for “season”. It is driven mainly by the temperature difference between land and sea: in summer the land warms up more, moist sea air flows inland and releases its rain.

In detail

• Summer monsoon: Warm, moist air from the ocean moves over the land, rises and brings heavy, often days-long rainfall.
• Winter monsoon: The land cools down more than the sea, the wind turns and blows dry air from the land out to sea.
• Shift of the tropical rain belt: The Intertropical Convergence Zone moves north and south with the position of the sun and reinforces the pattern.
• South Asia: The best-known monsoon shapes India and its neighbouring countries; a large share of the annual rainfall falls there in just a few summer months.
• Other monsoon regions: East Asia, West Africa and northern Australia also have pronounced monsoon seasons.
• Importance for farming: Rice and many other crops depend on the rain arriving on time, and a weak monsoon can put harvests at risk.
• Risks: Heavy monsoon rain can trigger floods and landslides, while a failed monsoon can cause droughts.
• Variability: The strength and onset of the monsoon vary from year to year, influenced among other things by sea temperatures such as during El Niño.
• Effect on daily life: In monsoon regions festivals, travel seasons and working rhythms often follow the rainy and dry seasons (klimazonen-der-erde, meere-und-meeresstroemungen).