A drought occurs when there is shortage of rain for a particular period of time in a particular place !
Drought can be caused by too little precipitation (rain and snow) over an extended period, as most people assume, but drought can also be caused by increased demand for the available supply of usable water even during periods of average or above average precipitation. Another factor that can affect water supply is a change in water quality. If some of the available water sources become contaminated--either temporarily or permanently--that decreases the supply of usable water, makes the balance between water supply and demand even more precarious, and increases the likelihood of drought