Why it is sweating in summer eventhough the air is in unsaturated condition?

By unsaturated, I assume you mean 100% humidity -- raining or foggy.





Remember that the warmer air becomes, the greater its ablity to hold water vapor. So if you're going by reports of "relative" humidity, that doesn't tell you the whole story. If you had 75% RH at 0 degrees C versus 75% RH at 35 degrees C, the actual water vapor content of that air parcel would be much higher at the warmer temperature. Therefore, your body's abilty to sweat and cool itself (by evaporation) becomes harder with the increase in temperature, but a same RH as when it was cooler.





A better way of determining if its going to be uncomfortably humid or not is to observe the Dew Point temperature. That will give you a better indicator of how much moisture is actually in the air. Anything over a dew point value of 20-25 is generally quite humid!
Why it is sweating in summer eventhough the air is in unsaturated condition?
sweating has nothing to do with the humidity of the weather. it's a natural bodily reaction to high temperatures.





When your body is hot due to heat, the body response and works to make your body cool down. This includes dilating your surface blood vessels, and sweating or perspiration.
Why it is sweating in summer eventhough the air is in unsaturated condition?
Err... I'm taking you mean "Why do we sweat in summer even if air is not saturated with water"





If that's the case, then the reason is that the body produces sweat as a mechanism to cool itself down. This is because sweat absorbs heat from the body to change into vapor phase.





The reason of why you keep sweating when you're at the beach is that since air is already saturated, sweat doesn't vaporize and no heat is taken from the body, therefore causing more sweating.