Boots made of neoprene, a synthetic rubber, keep your feet dry and warm. You will find neoprene boots come in various thicknesses, mostly 3mm, 5mm, and 7mm. The thicker the boot, the warmer your feet will be. How warm you want your feet to be is a matter of preference- but 5mm is suitable for a temperature range of 43-53 F. However, if you plan to explore outdoors in colder weather conditions than this range, consider wearing 7mm thick neoprene boots.