Book excerpt: Weather and climate is a natural resource which is considered as a basic input in agricultural planning. It affects all the agricultural activities directly or indirectly. Agrometeorology is primarily concerned with the interactions among meteorological, hydrological and pedological factors that influence production systems in agriculture and allied sectors like horticulture, animal husbandry, fishery, forestry, etc. Thus the role of an agrometeorologist is to define all these interactions, to correlate physical environments with biological responses and apply the relevant meteorological skills to help farmers for exploiting weather conditions and improve agricultural production both in quality and quantity. In this backdrop, agrometeorology has been recommended as a core subject in the curriculum of B. Sc. (Agriculture), B. Sc. (Horticulture) and B. Sc. (Forestry) courses of the agricultural universities. Keeping this in view, this textbook has been written for the undergraduate students.