If you can afford the AC- Hostel fees then you should go with it because it is too hot especially from January to April in Chennai, but remember you have to share common mess there would be no separate AC-Mess for you.
If you can afford then there are few option by whom you can beat heat up-to few extent-
A) Take bath Multiple time especially between 8PM – 12 PM.
B) Go to Central Library stay there till 12 PM then come back ( Central Library is fully AC).
Last but not least Friendship with a person who Live in AC Hostel and stay with him.
enjoy machake #b2