| Weather Terminology |
| Wind Chill | The Wind Chill Temperature (WCT) index is an arbitrary "apparent temperature" comprising wind speed and air temperature. Stated simply, a cool day feels colder as the wind speed increases. Bodies and buildings tend to warm the air surrounding them and create a small layer of warmed air; winds tend to blow that warmed air away. WCT is only provided for temperatures at or below 50° F and wind speeds above 3 MPH. |
| Humidity | Relative Humidity is the ratio of water vapor contained in the air to the maximum amount of water vapor that can be contained in the air at the current temperature. |
| Dew Point | The Dew Point is the temperature at which moisture condenses out of air. Dew and fog are common forms. Dew results when a cold air mass moves across warmer ground or water, or when it confronts a warmer air mass. Fog forms when still, water-saturated air cools and water vapor condenses. At higher elevations, clouds and rain form. The Dew Point is similar to relative humidity, but expressed as a temperature. The air temperature must be at or below the Dew Point for moisture to condense. Other types are black ice, when dew or fine rain freezes on roads, and ground fog, which forms from autumn to spring in parts of the western U.S. |
| Barometer | Barometric Pressure is a measure of atmospheric pressure or the weight of air pressing down on the earth. Air in high pressure areas compresses and warms as it descends. The warming inhibits cloud formation and conditions are normally sunny (but fog and haze remain possibilities). Conversely, air in low pressure areas cools, expands and rises; clouds form and storms are a possibility. |
| Storm Rain | Storm Rain measures the amount of rainfall during an ongoing period of precipitation, regardless of the midnight cutoff associated with a 24-hour measuring period. Rain storm totals begin accumulating after two one-hundredths of an inch are recorded and continue until 24 hours have passed without measurable precipitation. |
| Wind Direction | The red pointer indicates the direction from which the wind is originating. A reading of "W" on the dial means the wind is coming from the west and is blowing toward the east. |
