June to September is monsoon season, when Lonavala sees heavy rainfall. If you don’t mind exploring with an umbrella in hand, then you will be rewarded with gushing waterfalls and glowing green surroundings.
Here is an article on a road trip to Lonavala you might enjoy reading - https://www.tripoto.com/lonavala/trips/lonavala-road-trip-itinerary-3495
Hope this helps.
Happy traveling :)
One of the best monsoon gateway, lush green mountains, waterfalls all across, mist, garam Bhutta and Lonavala chikki, life is beautiful....go to tiger hills, and drive till Sahara city, beautiful drive in rains