Dust Bowl - An extended period of exceptional drought that affected the Great Plains of North America during the 1930s. Agricultural activities were crippled during this epic drought. Heat waves and occasional dust storms were fairly common during the dust bowl years. On some occasions, the dust storms in the Plains made it all the way to the east coast.

Drizzle - A type of precipitation consisting of numerous tiny droplets of water less than 0.5 mm in diameter. Drizzle typically falls when there is fog or low stratus cloud cover over an area.

Altostratus Clouds - Are gray or blue-gray middle level clouds composed of ice crystals and water droplets. These clouds usually cover the entire sky. In the thinner areas of the cloud, the sun may be dimly visible as a round disk.

Aerosols - Tiny liquid or solid particles that become suspended in the atmosphere. Some sources for aerosols are volcanoes, wild fires, desert wind storms, and the burning of fossil fuels.

Short waves - Relatively small, short-wavelength ripples that occur in the mid to upper levels of the atmosphere. These are basically small-scale troughs that can produce bands of precipitation as they induce upward vertical motions. Short waves tend to move quickly along the prevailing winds and are a common occurrence in the vicinity of a jet stream.

Blue Moon - Term used when a full moon occurs twice in the same calendar month. It happens once every 2.7 years. An alternate definition is when the moon actually has a bluish tint to it caused by smoke or dust particulates in the atmosphere.

Celsius - A temperature scale in which zero is the freezing point of water and one hundred is the boiling point. This scale is directly based on the states of water at different temperatures. This is in opposition to the Fahrenheit scale which is based on alcohol and mercury thermometers.