Rainfall in Average Year

The precipitation maps shown here describe rainfall plus snowfall that reaches the land surface in an average year. Rain is the liquid form of water falling to the land surface where as Snow is the solid form of water. Both rainfall and snowfall are important sources of freshwater in the earth’s land-surface system.

It is the condensation of water vapour into clouds which become heavily laden with water that leads to rainfall events. A cooling of the air and also increased water vapour in the atmosphere generally act together in formation of rain clouds.

Precipitation is key to several other factors in the water cycle, namely runoff, soil moisture and evaporation. Season and climate zone are responsible for precipitation being rainfall or snowmelt, on a global scale.

Globally over a 12 month period there are clear patterns in the amount of water falling on the land surface. In high latitudes during winter months there is little precipitation from October to May. Whereas equatorial regions have a pattern with wet and dry seasons. Africa’s central and western regions show the movement of the rain zone from Eastern areas in January to central & Western regions by June/ July. The inter-tropical convergence zone (ITCZ) is the reason for this changing pattern. The ITCZ is a band of clouds circulating the earth near the equator, with solar radiation driving its movement.

  1. Average rainfall for Jan
  2. Average rainfall for Feb
  3. Average rainfall for Mar
  4. Average rainfall for Apr
  5. Average rainfall for May
  6. Average rainfall for Jun
  7. Average rainfall for Jul
  8. Average rainfall for Aug
  9. Average rainfall for Sep
  10. Average rainfall for Oct
  11. Average rainfall for Nov
  12. Average rainfall for Dec
  1. Map of average rainfall for January 1985 - 1999

    High rainfall in Amazon region of S. America

  2. Map of average rainfall for February 1985 - 1999

    High rainfall in Amazon region of S. America

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  3. Map of average rainfall for March 1985 - 1999

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  4. Map of average rainfall for April 1985 - 1999

    Increased rainfall in N. America and European region

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  5. Map of average rainfall for May 1985 - 1999

    Increased rainfall in N. America and European region

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  6. Map of average rainfall for June 1985 - 1999

    Rainfall concentrated to a narrow band in Africa

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  7. Map of average rainfall for July 1985 - 1999

    Rainfall concentrated to a narrow band in Africa

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  8. Map of average rainfall for August 1985 - 1999

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  9. Map of average rainfall for September 1985 - 1999

    Central and Western Africa start of wet season.

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  10. Map of average rainfall for October 1985 - 1999

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  11. Map of average rainfall for November 1985 - 1999

    Dry period in the Indian peninsula

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  12. Map of average rainfall for December 1985 - 1999

    Dry period in the Indian peninsula

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Google Earth View

Average Total Rainfall (mm/yr)

Bargraph referencing the colours on the rainfall maps.

Other Maps

Rainfall Maps