In 1805 Rear Admiral, Sir Francis Beaufort devised a method of describing the force of a wind with a relatively simple numbering system that indicated its various strengths.
The scale was modified in 1926 and relates to the estimated velocity and effects of the wind at around 10m above ground level.
Sir Francis' original scale was designed to determine wind force at sea and its effect on a Royal Navy ship.
He classified a force 2 wind as "that in which a well conditioned man-o-war, with all sail set and clean full, would go in smooth water from one to two knots." A force 12 wind was, "That which no canvas could withstand."