Tornadoes form when winds blowing in different directions meet in the clouds and begin to turn in circles.

VOA: special.2010.05.11

Clouds with extremely cool water are mixed with man-made ice crystals, such as silver iodide and metaldehyde crystals.

VOA: special.2011.01.11

It had to fly between huge thunderhead clouds on one side and Vietnam's airspace on the other.

VOA: special.2010.10.06

It began to form shapes. I could see clouds and wonderful trees and flowers.

VOA: special.2009.07.25

Some people say broccoli looks like small trees, and cauliflower like gathered clouds.

VOA: special.2010.03.09

They are painted with a design of clouds and stars.

VOA: special.2009.09.09

The nebulae,he said, were clouds of atoms and dust.

VOA: special.2009.04.29

So we all went up to the Space Needle to watch the fireworks and this big cloud moved in and covered the Space Needle and so we just kind of watched the clouds and that was it."

VOA: special.2010.07.02

The ash clouds include particles of rock, glass and sand that can get into an aircraft's engine and cause it to stall.

VOA: standard.2010.04.17

Pope Benedict denounced what he called "the clouds of evil" over Africa that have brought war and ethnic rivalry, reducing the poor to slavery and depriving "future generations of the resources needed to create a more solid and just society."

VOA: standard.2009.03.22

Friday started out stormy, but as the 14 soldiers, Marines and their families boarded a yacht for a sightseeing cruise around lower Manhattan, the dark rain clouds parted giving them a glorious view of the Statue of Liberty.

VOA: standard.2009.08.01