Second half of june may face heavy rains which may last more than a day with heavy lightning and thunder acompanied by heavy wind those winds make the trees dance. In remote areas electricity failure in winds will happen on a regular basis. Under direct sun light you will experience intense hotness due to high humdity. Its the right time to visit for enjoing all this add un umbrella/raincoat to your backpack. Find some methods to avoids leeches on ground trees/grass. One bottle of vodka will help you to enjoy the rain from your room. In Monsoon season all nights in Kerala is couple friendly
Kerela is lush green and refreshing in Monsoons. I had visited Kerela in July of 2015 and is undoubtedly spectacular. Also the house boats in Alleppey were Operational. However, I would suggest you enquire with the service providers in advance considering the floods in Kerela last year.