The tendancy for the middle regions of continents to have a wider temperature range than coastal areas.
(from the article `climate`) Continentality is a measure of the difference between continental and marine climates and is mainly the result of the increased range of temperatures ...
The distance between a site and open ocean water. Continental interiors (obviously!) and areas surrounded by nearly permanent, continuous sea ice are highly continental. 
the degree to which the climate of a region typifies that of the interior of a large landmass. Cf. oceanicity.