If all the moisture in the atmosphere was released as rain evenly all over the Earth, the water would cover the surface to a depth of only one inch or 25 millimetres.
Rainfall however, is definitely not even over the world. Some places like the tropics receive a lot more rain, and a lot more regularly, than other regions like the deserts.
In the polar regions, the temperature throughout the year is cold enough for rain to fall instead as snow. The cold air here however, is very dry, and the North and South Poles can be as dry as the hot deserts.
Temperate regions of the world like the British Isles receive regular rainfall, and they are neither too wet nor too dry. The presence of mountains however, can increase the amount of rain that falls locally