Cumulonimbus Clouds
	Thunder heads. At their most violent, they produce tornados. Their bases sometimes almost touch the ground, but their tops can rise to 75,000 feet and are often shaped like anvils (anvil clouds).
Stratus Clouds
	Blanket the sky in thick, dull-gray, low-hanging layers. They often produce drizzle or mist.
Nimbostratus Clouds
	Rain clouds. They form near the ground, and are dark. Sometimes you can actually see rain coming from them in long streaks that touch the ground.
Fog
	Forms close to the ground when moisture rises from the warmth of the earth into cooler air. It can occur over water or land.

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