Wall Cloud - A localized, persistent, often abrupt lowering from a rain-free base of a cumulonimbus cloud. The location of the wall cloud marks the location of a strong updraft feeding the storm. Therefore, many wall clouds exhibit rapid upward motion and sometimes rotation. However, not all wall clouds rotate. If the wall cloud is seen rotating, the formation of a tornado is possible.

Valley Breeze - A breeze that flows up a mountainside during the day. This upsloping breeze occurs due to the fact that the valley walls warm up faster than the higher terrain in the mountains. This makes the air in the valleys lighter than the air along the higher terrain of the mountains, making the air near the valley buoyant. The result is the upward breeze along the mountainsides during the day.

Rain Gauge - An instrument used to measure the amount of rainfall that occurs over a specific site. A standard rain gauge can measure up to 8 inches. The first known device that was used for measuring rainfall was invented in Korea in 1441.

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.

Hail-Spike - A radar signature that can occur when severe hail is present in a thunderstorm. The signature is seen as a narrow line of weak reflectivity beyond the thunderstorm. Its occurrence is due to the way the radar pulse is scattered in many directions when it reaches large hailstones. This phenomenon is also referred to as the three-body scatter spike.

Crepuscular Rays - The meteorological term used to describe rays of sunshine that poke through holes in the cloud cover. They oftentimes have a celestial quality to them.

Sundog - A colored luminous spot produced by refraction of light through ice crystals. Sun dogs are seen as bright spots that appear on either side of the sun. This optical phenomenon is also referred to as parhelion. They are most commonly seen during the winter season.