How accurate are bank & advertising thermometers?
Not very accurate!  It may seem hot, but its not as hot as shown here
at South Street and Normal Blvd. in Lincoln in early August 2000.

Large display temperature readings are rarely accurate for several reasons:
1.  They are not calibrated, or checked for accuracy on a regular basis as
     are the official National Weather Service thermometers.
2.  They are usually located above hot parking lots. 
3.  They can be exposed to the direct rays of the sun making them 
     even hotter.

There have been two official National Weather Service methods of measuring the air temperature. 

First, the instrument shelter and then, second, ASOS.
An official instrument shelter is shown on the left.  The temperature is taken inside the ventilated white instrument shelter at an elevation of about 4 feet off the ground and usually over a grassy surface.  An observer opens the door of the shelter and writes down the temperature observations.
ASOS is an acronym for "Automated Surface Observation System" and is used throughout the United States at all of our airport locations.  The instrument to the left, a hygrothermometer (only one of the many ASOS instruments) measures both the temperature and the dewpoint of the air and automatically sends the information to a computer for access by the National Weather Service.  Data are collected constantly as opposed to the old system of human collected hourly observations.

The above photo shows the total ASOS installation at Haines, Alaska.
Photograph by Tom Burgdorf

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