The climate of the United Kingdom is very mild as compared to its high latitude of more than 50 N. The reason is the influence of the North Atlantic Drift on this country.

The moderating influence of the warm Atlantic current known as the North Atlantic Drift in winter and the cool rain bearing systems which blow over the country from west to east in summer are the two factors that control the climate of the United Kingdom. The Northern part of UK is cooler than the southern part and the western part is rainier than the eastern part. So that Northern Ireland is much rainier than England and Scotland is cooler than both England and Wales.

The Southeastern part in which London is located lies in the rain shadow region so it receives much less rain than Fort William for example which lies on the windward side. London records about 600 mm ( 22 in, ) of rain annually and Fort William thrice as much. So the conclusion is that the south eastern part is both warmer and less rainy than the western or the northern parts. As the temperature remains uniformly cool throughout the year and the rate of evaporation is less so even 22 in. rainfall equally distributed over the year is sufficient to sustain deciduous forest and we find greenery every where in U.K. Northern Ireland receives so much rain that due to its vegetation it is called "the Emerald Island".

The temperature in U.K remains remarkably uniform. In London for example the warmest month rarely crosses 68 F (20 F) and the coolest rarely falls below 40 F (4 C ). Such a uniformity of temperature with uniformly distributed rainfall makes the climate equable and geographers call it lovingly as "the England type of climate" when they have to refer to any other place having the same climate e.g. North western France or Northeastern United states.

It follows from above that the climate of U.K remains mild both in summers and winters with substantial rainfall to sustain ample vegetation.