I started to ride more often about a year ago and I find that on longer rides (10-15km) that I fatigue a lot easier now that it is heating up. Is there anyway for me to stay cooler so that I don't fatiuge as easily.

I live in Atlanta, Georgia, USA where summers are hot and humid.

One thing I do is keep my drinks cool. Cool liquid in your stomach does a great deal to beat the heat, just like drinking hot coffee can warm you up on a cold day.

Even pouring water on yourself can work wonders.

Airflow is good for keeping you cool. Ride faster.

To help with the fatigue, be sure and eat before and during the ride. Also, drink plenty of water! Water is power when you are riding.
Also, cycling clothes are designed to help keep you comfortable in hot weather, so if you aren't wearing them now, you should think about those too.
And, the more you ride, the better your endurance will be, and the fatique will pass. Just keep at it!

Hopefully you wear a helmet. The airflow through the vents cools your head much better than wearing a cap. Not the best reason for wearing a helmet though!

Water, water, and more water. If you ride with a group, take a sip of water each time anyone else takes a drink. I try to take a sip every few minutes. I personaly drink just under 50oz of water on my daily ride (22miles).

Another thing you should never go without, is sunscreen. It is proven that sunscreen can reduce skin temp by 20 degreesF! I use an SPF 15 sunscreen on all my summer rides.

I live in Central Florida and I have lived near Atlanta. Central Florida during the summer is even worse.

Rule 1) Drink a lot of water. Top off before riding and drink while riding.

Rule 2) Cool clothes and sun screen.

Rule 3) Backing off the pace a tad may keep you feeling a little cooler.

Here is the rationale. When you get hot, the body diverts blood flow to the skin in an attempt to vent heat. I have found that riding at high altitude in Colorado (up to 12,000') is no more taxing and maybe less so then riding in hot, humid FL.

The extra blood flow to the skin means the muscles are getting less and maybe that is causing your sensation of "fatigue".

I was watching cable the other day and there was some kind os cooling vest. has any tried these?

Yes I do wear a helmut and bike clothes. But the summers here are hot!!!

Charlie, can you give us more info on this cooling vest? I have a light weight sleeveless jersey i sometimes wear, its great for the really hot days.

Where are you located?