Yellowstone National Park
Credit: Jeff Foott / Getty Images

The temperature in Yellowstone is fairly comfortable during the summer and cold during the winter, but the water that shoots out of the park's spectacular geysers is piping hot, reaching about 400 F underground. It's closer to 200 F when it spews, but that's still more than hot enough to cause third-degree burns. There's a tragic true story about a man dying after trying to save a dog from Fountain Paint Pot, a beautiful hot spring named for swirling colors caused by oxidation. Keep your dog on a leash when you make the trip.