The USCRN rating system classifies the sites of weather stations with ratings from 1 to 5 (1 being the best)
From the USHCRN manual:
The USCRN will use the classification scheme below to document the “meteorological measurements representativity” at each site. This scheme, described by Michel Leroy (1998), is being used by Meteo-France to classify their network of approximately 550 stations. The classification ranges from 1 to 5 for each measured parameter. The errors for the different classes are estimated values.
- Class 1 – Flat and horizontal ground surrounded by a clear surface with a slope below 1/3 (<19deg). Grass/low vegetation ground cover <10 centimeters high. Sensors located at least 100 meters from artificial heating or reflecting surfaces, such as buildings, concrete surfaces, and parking lots. Far from large bodies of water, except if it is representative of the area, and then located at least 100 meters away. No shading when the sun elevation >3 degrees
- Class 2 – Same as Class 1 with the following differences. Surrounding Vegetation <25 centimeters. Artificial heating sources within 30m. No shading for a sun elevation >5deg.
- Class 3 (error 1C) – Same as Class 2, except no artificial heating sources within 10 meters.
- Class 4 (error >= 2C) – Artificial heating sources <10 meters.
- Class 5 (error >= 5C) – Temperature sensor located next to/above an artificial heating source, such a building, roof top, parking lot, or concrete surface.
Starting in 2007, the Surfacestations.org project undertook to make field inspections of weather stations to classify them according to the CRN criteria. The website provides the names of 23 stations that have the CRN#1 Rating for the quality of the sites, along with all stations that have been rated thus far.
As it happens, the CRN#1 stations are spread out across the continental US (CONUS): NW: Oregon, North Dakota, Montana; SW: California, Nevada, Colorado, Texas; MW: Indiana, Missouri, Arkansas, Louisiana; NE: New York, Rhode Island, Pennsylvania; SE: Georgia, Alabama, Mississippi, Florida.