There are a few key things to help you keep cool.
1. Keep Hydrated- It’s surprising how many people don’t drink enough fluid over the course of the day. In a hot climate you lose a lot of water through perspiration. I would avoid drinks such as beer or drinks with caffeine in (ie coffee, most energy drinks) as this will actually dehydrate the body. Caffeine and beer act as a diarrheic which will basically mean you have to empty your bladder more often. Aim for 2 litres of water a day. If very hot day 3 or 4 litres because of loss of fluids.
2. Wear cool clothes and light clothing which are cotton based. Polyester (which is in a lot of clothes as it is cheap) is not good for letting the skin breathe and can make you hotter. Go for 100% cotton if you can.
3. It works for some people but try drinking hotter drinks such as tea (jasmine, green tea etc) as this raises the temperature of your hypothalamus (inner body temperature regulation system) meaning your body acclimatises to hotter surroundings a little easier. Think of it like if you had a really cold bath, then stepped outside how hot you body feels because it is used to the cold.
Hope it helps:-)