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Have you ever asked yourself why some areas of the world are deserts and others covered in ice and snow? Why do some countries have rainforests full of life while others have different types of forest and wildlife? It is climate that controls the type of environments, habitats, vegetation and wildlife that surrounds us.

Different countries and environments around the world have varying climate and weather conditions. You may have been on holiday to a country that is much hotter than the United Kingdom. If you are going skiing it is a good idea to visit a country with snowy mountains!

The world can be divided into 4 main climatic zones depending on how hot, cold and wet it is in an average year.

The Equatorial or tropical zone
The Arid sub-tropical zone
The Temperate Zone
The Polar Zones


Map of World Climate Zones (Metoffice)

equatorial zone

The climate at the equator is known as the equatorial or tropical zone. Most regions along the equator have very hot and humid climates. Rainfall can be excessive and at certain times of the year thunderstorms can occur on a daily basis. Annual rainfall is normally in excess of 2000mm with heavy showers on most afternoons. This pattern of rainfall is due to wind patterns, which creates ideal conditions (warm, moist, unstable air) for the formation of storm clouds. The temperature usually ranges little from about 26ºC - 28ºC. During any ‘drier’ season temperatures can reach 33 ºC. At night the cloud cover can act as a blanket keeping temperatures to approximately 22ºC. The equatorial/tropical zone includes the Amazon Basin in Brazil and its famous rainforest, West Africa’s Congo Basin and Indonesia.
rainforest
The Costa Rican Rainforest (NOAA)

To the north and south of the equatorial/tropical zone lies the sub-tropical zone. In this zone there is not enough rainfall for vegetation to survive. What little rain does fall supports sparse, scrub vegetation. Less than 250mm (10inches) of rain falls each year, and it is possible for a year to pass without any rainfall at all. Areas in the sub-tropical zone will have clear skies due to high pressure and stable descending air. Temperatures can often reach a maximum of 40-45ºC, though at night can drop to near freezing. The Sahara, Saudi Arabia, large parts of Iran and Iraq, North West India, California, South Africa and most of Australia.
desert
Red Rock Canyon, Nevada, USA

temperate zone

Temperate Climate includes those countries with small fluctuations in temperature all year round and rainfall that can fall throughout the year. Temperate climate conditions are usually between latitudes of 40º and 60º north and south of the equator and include temperate grasslands and deciduous forests. The United Kingdom is included in this climate zone, in addition to most of Europe, parts of North West and North East America, Eastern Asia and Southern Chile. However, within these regions several different types of weather may occur depending on an area’s location in relation to oceans and large landmasses. Temperate zones only cover 7% of the World’s land surface, but they are seen by many as the best place to live. With mild temperatures and a good rain supply countries with a temperate climate are home to four-tenths of the world’s population.
lake
Lake view at Canterbury Environmental Education Centre

polar zone

Polar zones are always covered with snow and ice as the sun is never high enough to allow melting and temperatures hardly ever climb above freezing. A polar climate is extremely cold and dry. Less that 250mm (10inches) of precipitation a year falls in places making some polar regions as dry as the deserts of the world. A minimum temperature of -88ºC has been recorded at Antarctica. The Arctic and Antarctica are obvious regions within the Polar Zone, however other parts of the world are also included. The Arctic actually includes the ice-covered part of the Arctic Ocean, Greenland and much of Northern Canada and Northern Siberia. The Antarctic Continent is covered by ice that can be several kilometres thick.
antarctica
Antarctica (NOAA)