Variability of rainfall and effective onset and length of the monsoon season over a sub-humid climatic environment

► Mean annual rainfall varies from 1137 mm at Patna to 1219 mm at Sabour. ► July is the rainiest month in all the zones followed by August. ► Maximum increase in annual rainfall at Sabour (40.1%) and minimum at Patna (10.1%). ► Mean effective onset of monsoon 18th June at Sabour to 28th June at Patna. ► Trends in the date of effective onset tend to be early in all the sites except Madhepura.