To help control body temperature, my wife and I have little neck bags that we wear. After soaking in cold water for about half an hour, the gel crystals absorb water, expand and then stay cool for 3 or 4 hours, providing some nice relief. We carry an extra set in ziplock bags packed with ice water so we can swap them out during the day. Of course, in areas with high humidity, these types of evaporative cooling methods (neck bags, vests, etc) don’t work as the air is already close to saturation.
On solo trips I’ve made frequent stops to refill my hydration pack and douse my head, and have even resorted to wearing a soaked cloth under my helmet. You are probably thinking mesh gear is the answer on hot days, but that has the downside of too much evaporation - leading to dehydration - if you don’t make sure to drink a lot.
Mary has also got quite adept at holding a water bottle as we ride and occasionally dumping some down inside my collar as well as her own. This little jolt of refreshment was most welcome when we were riding across Nebraska at 38 degrees a couple years ago. Once the bottle was emptied, a quick stop to pull another out of a pannier let us continue.
Heading out early to get most of your riding done before the hot part of the day arrives is another option.
We will soon be able to buy a little device that will help keep us both warm and cool. A company called Core Temperature Controls, based in Virginia, is close to releasing a nifty little device that uses thermoelectric plates and a digital temperature controller to provide both heating and cooling. Just think what this unit could do to the selection of riding gear in your closet.
A few links:
Ride responsibly and enjoy your travels.
-- R. Bruce Thomas