| Term | Definition |
| precipitation | any form of water that falls from clouds and reaches Earth's surface |
| drought | long periods of unusually low precipitation |
| cloud seeding | sprinkling of chemicals into clouds to try to produce rain |
| rain guage | an open-ended can or tube that measures the depth of rain that falls |
| rain | drops of water at least 0.5 millimeter in diameter |
| sleet | ice particles smaller than 5 millimeters in diameter |
| freezing rain | raindrops that freeze when they touch a cold surface |
| snowflakes | when water vapor in a cloud is converted directly into ice ctystals |
| hailstones | round pellets of ice larger than 5 millimeters in diameter |