If you are planning on doing a triathlon this weekend and race conditions are predicted to be boiling hot, consider putting ice in a small ziplock baggie. Keep the ice in a small, soft-sided cooler in the transition area. When you change from bike to run, take a few seconds to retrieve the baggie from the cooler and then put the ice bag under your hat or down the front of a swim suit or tri suit.
You can move the baggie around to keep yourself comfortable and not freeze your skin. For the races with ice on the course, you can refill the baggie with fresh ice when yours melts. For courses with no ice available,
just dispose of the baggie at the aid station trash can.
For those of you that struggle in the heat, this is a great trick.