Majorly there are 3 seasons like most of India in Deoghar . Summers are extreme hot season when outdoor activity in Deoghar is almost impossible. Monsoon and winter is good time to visit Deoghar when weather is cool and comfortable for outdoor activity.
Though a bit unpleasant for foreign tourists, Deoghar attracts huge crowds of domestic travelers during monsoon especially in Shravan (August).
Summer - April-June
Best Time to visit Deoghar - July - August (Shravan) for Kawar Yatra
Temperature in Deoghar - 22°C - 30°C