Mammoths, lions and camels once roamed along wetlands just north of what is now known as Las Vegas, Nevada, and their history is preserved at Tule Springs Fossil Beds National Monument. The area now draws winter refugees from states hit hard by icy weather, while sunbathers spend summers in temperatures above 110 degrees F. It generally receives less than five inches of annual rainfall, and water temperatures may range from 45 degrees F. in winter to 85 degrees F. in summer.