If you are planning to the southern most end,like Ponmudi hills of Thiruvananthapuram its the right time. The hills are completely fogged up and its a mind blowing sight.Monsoon is not much strong this year. I surely suggest this as the right time to visit.
If your interested to visit hill station,waterfall,thick green forests,wildlife tourism july,aug,sep is better .and prices of accomidation also very low,less crowd... oct,nov,dec season time price of accomidation is very high in summer you can enjoy more through travelling in backwater every season has their unique feature so.......
Post monsoon say from Mid Aug till Feb is the ideal time to visit Kerala. If you plan your journey during Aug, you can witness almost all waterfalls in its full glory and yes it's humid all around the year. Post September the entire region becomes more greener and fresh, thanks to Monsoon. Nov to Feb the temp will be at its lowest and very much ideal for sightseeing.
Best season to visit Kerala is from October to April. Weather during this season is pleasant and mild.Traditionally the period from October to February is the peak season for holidays in Kerala. However you can visit during monsoon season between June and August too.