Weather Definitions
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Readings shown on the Weather Observations Page are:

BAROMETRIC PRESSURE - The weight of the air that makes up our atmosphere exerts a pressure on the surface of the earth. This pressure is known as atmospheric pressure. Barometric pressure changes with local weather conditions, making barometric pressure an extremely important weather forecasting tool. High pressure zones are generally associated with fair weather; low pressure zones are generally associated with poor weather. However, the change in pressure is usually more important. In general, rising pressure indicates improving weather; falling pressure indicates deteriorating weather conditions.

DEWPOINT - Is the temperature to which air must be cooled for saturation (100 percent relative humidity) to occur, providing there is no change in water vapor content. Dew point is an important measurement used to predict the formation of dew, frost, and fog. i.e., if the dew point and air temperature are close together in the late afternoon when the air begins to turn colder (near 90 to 100 percent humidity) fog is likely during the night.  It is also a good indicator of the air's actual water vapor content.  High dew point indicates high water vapor content; low dew point indicates low water vapor content.

EVAPOTRANSPIRATON (ET) - Is a measurement of the amount of water vapor returned to the air in a given area. It combines the amount of water vapor returned through evaporation (from wet vegetable surfaces and the stoma of leaves) with the amount of water vapor returned through transpiration (exhaling of moisture through plant skin) to arrive at a total. Effectively, ET is the opposite of rainfall, and is expressed in the same unit of measure (inches). This weather station uses air temperature, relative humidity, average wind speed, and solar radiation data to estimate ET, which is calculated once each hour.

HUMIDITY - Refers to the amount of water vapor in the air. However, the amount of water vapor that the air can contain varies with air temperature and pressure. Relative humidity takes into account these factors and offers a humidity reading which reflects the amount of water vapor in the air as a percentage of the amount the air is capable of holding. Relative humidity, therefore, is not actually a measure of the amount of water vapor in the air, but a ratio of the air's water vapor content to its capacity.

RAIN - Five different totals are displayed:

Daily Rain - 24-hour total rain, beginning and ending at midnight.

Month Rain - Displays total rain measured during the current month.

Rain Rate - During a rain event, the Rain Rate calculates the total  amount of rain that would be measured if the current rain intensity would remain constant over the next 1-hour period.  This measurement is used to predict flooding.

Year Rain - Displays total rain measured during the current year.

SOLAR RADIATION - What we call "current solar radiation" is technically known as Global Solar Radiation, which is a measure of the intensity of the sun's radiation reaching a horizontal surface. This irradiance includes both the direct component from the sun and the reflected component from the rest of the sky. The solar radiation reading gives a measurement of the amount of solar radiation hitting our weather station's solar radiation sensor at any given time, and is not affected by snow. Measurements are expressed in Watts/sq. meter.

TEMPERATURE - Three temperatures are displayed. 

Wind Chill - Takes into account how the speed of the wind affects our perception of the air temperature. Our bodies warm the surrounding air molecules by transferring heat from the skin. If there's no air movement, this insulating layer of warm air stays next to the body and offers some protection froom cooler air molecules. However, wind sweeps that comfy warm air surrounding the body away. The faster the wind blows, the faster heat is carried away and the colder you feel.

Heat Index - Uses temperature and the relative humidity to determine how hot the air actually  feels. When humidity is low, the apparent temperature will be lower than the air temperature, since perspiration evaporates rapidly to cool the body. However, when humidity is high, the apparent temperature feels higher than the actual air temperature, because perspiration evaporates more slowly.

Temperature-Humidity-Sun-Wind (THSW) Index - Uses humidity and temperature like the Heat Index, but also includes the heating effects of sunshine, and the cooling effects of the wind to calculate an apparent temperature of what it feels like out in the sun.

UV (ULTRA VIOLET) RADIATION - Energy from the sun reaches the earth as visible, infrared, and ultraviolet rays. Exposure to UV rays can cause numerous health problems, such as sunburn, skin cancer, skin aging, cataracts, and can suppress the immune system. Our weather station analyzes the changing levels of UV radiation, and can help advise of situations where exposure is particularly unacceptable. The observation reading is given as a UV Index, which is an intensity measurement first defined by Environment Canada and since adopted by the World Meteorological Organization. The UV Index assigns a number between 0 and 16 to the current UV intensity. The lower the number, supposedly the lower the danger of sunburn. The measurement shown on this website is a real-time measurement measured by the UV sensor on the weather station.

WIND SPEED AND DIRECTiON - The weather station calculates and displays a 2-minute average and 2-minute dominant wind direction.