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Please note: Due to scheduled maintenance, many NCEI systems will be unavailable Wednesday, June 16th between 6:00 AM ET - 8:00 AM ET.

Automated Surface Observing System (ASOS)

Automated Surface Observing System (ASOS) units are automated sensor suites that are designed to serve meteorological and aviation observing needs. There are currently more than 900 ASOS sites in the United States. These systems generally report at hourly intervals, but also report special observations if weather conditions change rapidly and cross aviation operation thresholds.

ASOS serves as a primary climatological observing network in the United States. Not every ASOS is located at an airport; for example, one of these units is located at Central Park in New York City. ASOS data are archived in the Global Surface Hourly database, with data from as early as 1901.