The factors controlling the amount and rate of evaporation are : (i) temperature; (ii) the moisture content or the degree of dryness or aridity of air; and (iii) movement of air.

(1) Increase in temperature increases the water absorbing capacity of the given column of air and vice versa.

(2) When and where aridity is high, air has a potential of absorbing and retaining a large amount of moisture. In air with higher humidity, this potential is reduced; hence evaporation is slow and small in amount. Evaporation is greater on the oceans in summer than in winters.

(3) The greater the movement of air, the greater is the evaporation. The movement replaces the moisture filled layer by a drier layer which has a larger capacity of absorbing moisture.