i'm in india and it's winter here the room temp is 25c
Then you need a cooler. In summer the temperature are very high(at least in my area reaches about 46 degrees), so you cannot expect the hard drive temperatures to be any lower than that.
The max temperatures I ever got was 54 degrees c in summer. I never installed a cooler and neither did the hard drive caused any issues.
You need to air flowing in your cabinet like maestro said. You need to have a fan placed on the front of the case which directly flows air to the hdd. Any warm air stagnation can increase your temperatures dramatically.