Heat and rain, all year

The climate

The Met Office describes the Koppen climate classification as one of the most widely used systems of climate zones, dividing climates into five groups based on rainfall and temperature, including tropical climates (A). Met Office Tropical climates, in Met Office wording, are close to the equator and have high temperatures and rainfall. Met Office

The Met Office finds tropical rainforest climates in South America, Africa and South-east Asia. Met Office Lying either side of the equator, tropical rainforest climates are characterised by high temperatures and year-round rainfall. Met Office Average temperatures are usually around 20-30 °C, with minor variation over the year. Met Office Rainfall is over 60 mm of rain in every month, giving rise to thick rainforest and some of the highest densities of biodiversity seen on land. Met Office

The climate in these regions is one of relatively high humidity with no marked seasonal variation. Temperatures remain high, usually about 30 °C (86 °F) during the day and 20 °C (68 °F) at night. Britannica

The rainforest biome remains warm all year and must stay frost-free. The average daily temperatures range from 20°C (68°F) to 25°C (77°F). NASA NASA says rainforests receive the most rain of all of the biomes in a year, and that a typical year sees 2,000 to 10,000 millimeters (79 to 394 inches) of rain. NASA

Tropical regions also contain other climate zones, which are hot but have distinct dry seasons, unlike rainforests. Met Office Tropical monsoon climates have a season of heavy rainfall, connected to a seasonal change in wind direction. Met Office Tropical savannah climates have a more pronounced dry season than monsoon areas. They also have grasslands, rather than rainforests. Met Office

For countries nearer the equator, the Met Office says, seasons become defined by wetter or drier weather, as the temperatures vary little during the year. Met Office Usually, countries located close to the equator with tropical climates have only two seasons, the dry season and the wet season. Met Office During the wet season there is typically heat build up over the course of the day, allowing thunderstorms to grow and eventually produce rain in the afternoon, continuing overnight. Met Office

The ITCZ

The Intertropical Convergence Zone, or ITCZ, is a band of low pressure around the Earth which generally lies near to the equator. Met Office The trade winds of the northern and southern hemispheres come together here, which leads to the development of frequent thunderstorms and heavy rain. Met Office These thunderstorms can reach, and sometimes exceed, 16 kilometres, 55,000 feet or 10 miles in height above the surface. Met Office

The resulting circulation, with air converging near the surface around the equator and diverging above, is known as the Hadley Cell. Met Office The ITCZ moves throughout the year and follows the migration of the Sun's overhead position, typically with a delay of around 1-2 months. Met Office In July and August, the ITCZ lies well to the north of the equator over Africa, Asia and Central America before moving south into South America, central Africa and Australia by January and February. Met Office

Another term for the ITCZ, used historically in seafaring circles, is the doldrums, since the winds along the band of low pressure are typically calm. Met Office