First things first, when running, wear a sun visor or a pair of sunglasses to keep direct sunlight from your face. When under extreme weather, you will need all sorts of shade you can get from-- be it from trees, from tall buildings, from your hat, sun visor or shades.
Bring a bottle of water with you all the time. This is pretty much a given especially during sports events. You need to stay hydrated throughout the whole course should you wish to keep running for a longer period.
cooling gear to keep yourself from sweating too much. Avid runners highly suggest the use of cooling gear, so you stay hydrated and stay cool while running.
Although this is not a running-related tip, it would still be wise for runners like yourself to be familiar with the symptoms and first aid care in the event of heat stroke. Heat stroke grounds runners especially during marathons. Your basic knowledge in heat stroke prevention could save a life.