Weather Stations are facilities or locations where meteorological data
are gathered, recorded, and released. Such stations are of the
first order when they make observations of all the important ... elements either hourly or by self-registering instruments; of the
second order when only important observations are taken; of the
third order when simpler work is done, as to record rainfall and
maximum and minimum temperatures.
[Source: Webster's Revised Unabridged Dictionary, ? 1996, 1998 MICRA, Inc]