I visited Hampi in mid May, everyone was advising me the same that Hampi will be very hot so avoid going to Hampi in May, but still I take a chance and result was amazing. Temperature in Hampi was 43,but you wont feel heat because the monuments in Hampi mesmerize you. i used to go for sight seeing at 7 in morning, come back to my room at 1 and again roam in Hampi between 4-8. The awesome thing of visiting Hampi in off season is that all the places are left to you only. There will be very less crowd to disturb you.
Hampi is very hot now a days. Actually ever place in karnataka including hill stations are also very hot. So its a big no to viist hampi this time. In varkala there is not much issue during this season because of the wind, which makes things easier in hot sun also