Rainfall is another metereological parameter that could get affected due to air pollution. The average annual rainfall in our state is 950 mm. The climate, by and large, is hot and humid. Hyderabad, however, can be hot and dry in the peak summer month. Our state is principally fed by the south-west monsoon while the north-east monsoon contributes about a third of the rainfall. Strong surface winds with velocities of 15 to 20 kmph blow in June-July from westerly and south westerly directions. High humidities ranging from 60-80 percent prevail during the south-west monsoon period. Thunderstorm occur during the pre-monsoon period, decreasing with the onset of south-west monsoon. They become more frequent in September-October with hazards of lightening particularly in rural areas.