1. Hat- A hat performs several duties during hot weather running. The bill adds shade for your face. Using a running hat with wicking properties will keep some of the buckets of sweat off of your face.
2. Moisture wicking clothes- Heat and humidity can produce TONS of sweating, so keeping it off your body will aide in cooling your body. Also, make sure that your clothes are designed or fit so you don't get chaffing.
3. Moisture wicking socks- A lot of us don't give much thought to our socks, but they are basically the underwear for our feet. They need to provide adequate support and keep your feet happy on those long runs. A blister on my foot is possibly one of the sure fire things that will make me cut a run short. My favorite socks are from lululemon and target.
4. Sunblock. Runners are so exposed to the sun so protect yourself. I've completely embraced my inner casper and I'm proud to be pale. Remember your skin gets more brown from the sun because of sun damage and, to get super geeky, it puts kinks in your DNA which causes mutations which = cancer. You can see from the pic I use SPF 70, and it's waterproof so I can't sweat it off. Hopefully, I made the point- protect your skin!
Runner's world has some great information on running in the heat. Remember, humidity can make you sweat so much more and you have to think about that when rehydrating. I love coconut water flavored with mango or pineapple for some natural hydration/electrolyte supplementation (or yummy fruit smoothie....see previous post) after a hot run.
As a fun note....this is my 100th post...hooray for milestones!