Question

how are drought occur

Answer 1

Droughts happen when there is not enough rain for a long period of time. It's not like a dry spell - there is so little precipitation (rain, snow, sleet or any kind of moisture) that a whole region starts to dry out. Sometimes a drought takes decades to develop fully and they are very difficult to predict.

Answer 2

when there is shortage of rain and it lead to drought and drought leads to crop failure