Hi Yashwanth,
Like all beach destinations, the monsoons will make Gokarna's beaches unpleasant. However during this season the Western Ghats are beautiful with greenery at its full bloom. And there are many treks into the Western Ghats that you will be able to enjoy at this time.
I am attaching this link with an amazing compilation of all things Gokarna:
https://www.tripoto.com/gokarna
Hope this helps!
Happy traveling,
Senneil
Monsoon season in Gokarna is from June to September. Monsoon is usually off season. Monsoon rains will be quite heavy and that might make travel and sightseeing plans difficult. Best time to visit Gokarna would definitely be from October to March, when there is pleasant and warm weather!!
Its totally depend on your luck... if its raining you would be not able to explore it; however, during this time weather would be nice to just to enjoy and relax in a good resort/stay.