Silex Spring, a turquoise colored pool near the start of the trail at Fountain Paint Pots in Yellowstone National Park has an average temperature of 174.7°F according to the National Park Service. It emits a constant cloud of steam and in the extreme cold of winter, the steam settles on the surrounding trees and freezes into a thick frosting like coating. Although this images appears to be black and white, it is actually a color image.