NOAA (weather.gov) : NOAA; Earth Science Office
Weather in the United States, in the visible (in daylight) and infrared (night) channels.
"The visible image is the equivalent of taking a
black and white photo of the earth. The bright areas show where the sun is being reflected back into space as a result
of clouds or snow cover. Clouds and snow show up white. The thicker the cloud, the brighter the color. Land surfaces show
up as gray and ocean surfaces nearly black. The major limitation to visible imagery is that it is only valid during daylight.
The infrared image shows heat based radiation from the infrared spectrum. In other words, the warmer the surface, the more infrared radiation it emits. For a satellite image, cooler surfaces are bright and warmer surfaces are dark. Since the atmosphere cools as you increase in altitude, clouds would show up as bright areas and land surfaces as dark areas. In addition, low clouds will be more gray and higher clouds will show up more white. Tall thunderstorm clouds will show up as bright white and fog will be hard to decern from land areas. A large advantage of IR is that you can view it 24 hours a day."
(source: http://weather.unisys.com/satellite/details.html)
source: weather.com
Weather in infrared.
source: weather.com
Radar (Full resolution version loop (3400x1700 pixels - 2.2mb))
source: weather.gov