Sounds like dehydration and heat exhaustion to me. We get temperatures over 85 for about 3 months of the year, and honestly the best thing to do is avoid training during the hot part of the day. Train either early morning or whack on some lights and go out at night. Some days here it gets so hot (around 115) that I train on the wind trainer under the airconditioner.

Heat exhaustion/stroke is an awful feeling and when it does happen I would recommend going for a cold shower and drinking plenty of water.