An important point to remember if you like spending time out in the (0) OPEN air is that the human head doesn't work very well outdoors if it becomes too hot, cold or wet. That's why a hat is a good investment, wherever you're planning to go out and (1) ............. Surprisingly, a single waterproof hat with a brim will do the (2) ............ adequately in most conditions. In cold climates, the problem is that the head is (3) ............ heat all the time. As (4) ............ as fifty to sixty percent of your body's heat is lost through the head and neck, (5) ............ on which scientist you believe. Clearly this heat loss needs to be prevented, but it's important to remember that hats don't actually (6) ............ you warm, they simply stop heat escaping. Just as important is the need to protect your neck from the effects of (7) ............ sunlight, and the brim of your hat will do this. If you prefer a baseball cap, (8) ............ buying one that has a drop down 'tail' at the back to stop your neck getting sunburnt. And in wet weather conditions hats are often more practical than pulling up the hood of your waterproof coat because when you turn your head, the hat goes with you, whereas the hood usually does not.