Jet Stream - Intense winds that are concentrated in a relatively narrow stream in the upper atmosphere. Most jet streams are found at around 30,000 ft up in the atmosphere. The two jet streams that impact the US are the polar and subtropical. Both act as highways for weather systems to travel along.

Astronomical Twilight - Is defined to begin in the morning, and to end in the evening when the center of the Sun is geometrically 18 degrees below the horizon. Before the beginning of astronomical twilight in the morning and after the end of astronomical twilight in the evening, scattered light from the Sun is less than that from starlight and other natural sources. Before and after astronomical twilight, the sky is absolutely dark.

Trough - A sharpened zone of cyclonic wind change usually associated with a zone of lower pressure. Troughs can occur at the surface up to around 30,000 ft up in the atmosphere. Deep troughs in the mid to upper levels tend to be associated with surface frontal boundaries and surface low pressure systems. Inclement weather can be expected when a trough moves through a particular area.

Horse Latitudes - Areas of calm or light and variable winds located between 30 and 35 degrees north and south of the equator. This region's weather is influenced by converging air flows aloft from the tropics, thereby creating regions of high pressure at the surface. Hot and windless conditions can last for weeks at a time in the horse latitudes. When ships would travel to the New World, this region was known for creating delays in shipping that could create food and supply shortages for merchant ships.

Transpiration - The process by which water escapes plants into the air and turns into water vapor. The rate at which plants lose water to the air increases as the temperature increases. Corn plants transpire at a rate higher than most plants. This means that corn needs more moisture to survive compared to most plant life.

Roll Cloud - Also known as a shelf cloud. This cloud formation is seen when a solid line of thunderstorms approaches. These low hanging clouds cover the entire horizon and are seen as a cylindrically shaped and elongated cloud. They occur along the gust front of a line of storms as one can expect winds to increase noticeably as these clouds head through.

Hiver - Hiver is the French word for winter.