Continentality is a measure of the degree to which the climate of a region typifies that of the interior of a large landmass. Such regions usually experience hot summers and colder winters, being far away from the moderating influence of the ocean, which keeps climates milder in winter and cooler in summer. This is because soil and rock have a much lower heat capacity than water, and therefore gain and lose heat much more quickly. Continental climates are often found to be relatively dry. Most of the moisture carried by air masses originating over ocean regions far away is lost as rainfall earlier in its journey.
Regions of the Earth that have continental climates include Siberia and central Russia, and much of North America. Siberia, Canada and the northern states of the US in particular can exhibit very large differences between summertime and wintertime average temperature of up to 40°C. This compares to the more maritime climate of the UK, where the annual average temperature range is only 10°C.
Air masses that originate from continental interiors sometimes influence continental fringes that usually experience maritime climates. In the UK, continental polar air in winter is very cold and temperatures associated with this air stream are usually well below average. The air mass is basically very dry and stable but a track over the central part of the North Sea supplies sufficient heat and moisture to cause showers, often in the form of snow, over eastern England and Scotland. During summer, the airflow is usually warmer, since even northern parts of Europe experience high temperatures during this time of year.