Take into account the culture
Every organization has a particular culture, so it is recommended that you follow the undefined rules as well and consider the norms before you select your dresses. You have got to use your common sense while dressing as high temperature does not give you the license to wear extremely short skirts or to show cleavage. You must be reasonable in your dressing, in order to look sophisticated and graceful.
On the other side of the coin, you should not be overdressed as well, as it looks extremely awkward in summers. Maintain a balance and try to avoid business suits and formal shoes, when everybody else is wearing khakis and sandals.
Footwear is very important in summers. Choose the shoes/sandals according to the shape of your feet and make sure they are comfortable. Don't wear anything too flashy or bold, keep it simple.