In meteorology, haar is a coastalfog. Haar is typically formed over the sea and is brought to land by wind advection. This commonly occurs when warmer moist air moves over the relatively cooler North Sea causing the moisture in the air to condense, forming haar. Sea breezes and easterly winds then bring the haar into the east coast of Scotland and North-East England where it can continue for several miles inland. This can be common in summer when heating of the land creates a sea breeze, bringing haar in from the sea and as a result can significantly reduce temperatures compared to those just a few miles inland.
The term haar is used along certain lands bordering the North Sea, primarily eastern Scotland and the north-east of England. Variants of the Scots term include har, hare, harl, harr, hoar and the origin may be Low German/Middle Dutch hare or Saxon. In Yorkshire and Northumberland it is commonly referred to as a sea fret.