An evaporative vest, such as the Rev’It Liquid Cooling Vest pictured enhances the process by absorbing and storing water, then releasing it over time. For best results, you’ll need a mesh jacket with air flow. When worn together the effect is truly refreshing on a hot summer’s day. Evaporative vests are available from apparel manufacturers from Alpinestars to TechNiche in a variety of sizes, styles, colors and prices.
Or, if none of that does it for you, like if you live in Southern Arizona, there's always this monster cooling (AND heating) system
EntroSys BikeAir rider climate control system – fancy speak for mobile air-conditioning. The system straps to the rear seat or luggage rack, is powered by the motorcycle’s battery and is controlled via a wireless key fob remote. Three levels of cool (or warm) air is delivered to an air-vest worn underneath your protective gear. The EntroSys retails for $1,500 plus shipping and handling. For more info or to order check out www.bikeairusa.com.