Climatological substation

From Glossary of Meteorology

climatological substation

A weather observing station operated by a cooperative observer (unpaid volunteer) for the purpose of recording climatological observations.

This is a unique category of stations in the United States (there are about 6000 of them), but it compares to the third-order climatological station as defined by the World Meteorological Organization.
Compare also second-order climatological station.