A designation for the sky cover when the sky is completely hidden by an obscuring phenomena such as fog or smoke.

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The temperature at which all molecular motion ceases, equal to -459.67 degrees Fahrenheit or -273.16 degrees Celsius.

An instrument for measuring wind force and speed.

A glow of colored lights in the northern and southern skies, caused by electrically-charged particles streaming out of the Sun and entering the Earth’s atmosphere.

An instrument for measuring atmospheric pressure, used in weather forecasting and in determining elevation.

A system for estimating the wind speed by observing the state of the sea, using a scale on which successive ranges of wind velocities are assigned code number from 0 to 12, corresponding to categories form calm to hurricane. Devised by British Admiral Sir Francis Beaufort (1774-1857)

A violent winter storm with winds about 32 mph/ 51 kph, and visibility less than 500 feet/ 150 meters because of falling and blowing snow. Sometimes "ground blizzard" is used to describe a storm in which all the airborne snow has been re-suspended from that which had previously fallen.

A condition of little or no wind.