According to a 2005 report by the National Highway Traffic Safety Administration, helmets were only 37 percent effective in preventing fatalities [source: NHTSA]. Nonetheless, most states enforce laws requiring motorcyclists to wear them while on the road.
Even in hot weather, wear a full-face helmet with a flip-down visor to protect from the elements and debris. Ensure that the helmet has ventilation and a breathable or removable lining.
To stay cool, wet your hair with water before starting every leg of your trip. And don't worry about overheating because of your helmet: A 2008 study published in the British Medical Journal determined that no more than 10 percent of body heat escapes through your head [source: Sample].