This loop contains the past 6 hours of images of the United States, one image per hour taken from a NOAA satellite. These images are taken in the infrared band of light and show relative warmth of objects. Colder objects are brighter and warmer objects are darker. Lower layers of clouds, generally warmer and lower in altitude, are colored gray. Colder and generally higher clouds tops are highlighted in colors. IR imagery is useful for determining cloud features both at day and night.