I think the monsoon season may have passed in Kerala in August and so you can try a relaxing weekend on a houseboat in the Kerala backwaters. For more information on houseboats look up
this page from
IndiaMike which has additional information on India.
The nearest airport is Kochi (COK) pervious known as Cochin. You can also stay at one of the many waterfront resorts in and around Kumarakom or at the Taj Malabar or the Brunton Boatyard resort in Kochi.