Official observations for Phoenix, AZ are measured at Sky Harbor International Airport with an ASOS. The ASOS (Automated Surface Observing Station) is a joint effort of the NWS, the FAA, and the DOD. The ASOS systems serves as the nation's primary surface weather observing network. It is designed to support weather forecast activities and aviation operations and, at the same time, support the needs of the meteorological, hydrological, and climatological research communities. There are currently more than 900 ASOS stations across the United States and its territories, and each one works non-stop, providing observations every minute of every hour of every day. Each station includes sensors to measure wind speed and direction, dew point, air temperature, precipitation type and amount, visibility, cloud height and thickness, and station pressure.
Typically, an ASOS will transmit a weather observation every hour. If weather conditions change, special off-hour observations are transmitted. Internally, the system is observing the weather far more frequently, generally every 10-20 seconds. Due to high variability in such short duration data, and to leverage quality control checks, the data are smoothed to longer temporal scales - on the order of minutes.
The data displayed on this page are based on the internal high-resolution one-minute data. From there, a standard rolling 5-minute average is applied to the temperature and dew point data. Precipitation data (1-minute) are accumulated. High (low) temperatures are the last observed instance of the maximum (minimum) value for the day.
JAN 1876 Weather observations start in Phoenix, conducted by the US Army Signal Corps. Instrumentation was located at Center Avenue and Washington Street. The first observation was made on January 28. Unfortunately, records during this period did not survive to present day.
JAN 1878 Observation equipment was moved slightly, to between Washington Street and Jefferson Street on Central Avenue on January 19, 1878.
AUG 1895 The US Department of Agriculture Weather Bureau, the predecessor to today’s National Weather Service, assumes responsibility for recording weather observations on August 6, 1895. The observation locations was moved to the Wharton Block roof on Central Avenue and Washington Street. Daily records from this period forward are available to this day.
AUG 1901 Observing equipment is relocated to the Talbot Building at the southwest corner of 1st Avenue and Adams Street.
MAR 1913 Observing equipment was relocated to the roof of the Federal Building at the southwest corner of 1st Avenue and Van Buren Street on March 24, 1913.
JUN 1916 Observing equipment was relocated to the lawn of the Water Users’ Building southwest of 2nd Avenue and Van Buren Street.
SEP 1924 Observing equipment was relocated to the Ellis Building courtyard at 2nd Avenue and Monroe Street on September 24, 1924.
JUL 1925 Observing equipment was relocated back to the lawn of the Water Users’ Building southwest of 2nd Avenue and Van Buren Street on July 18, 1925.
OCT 1936 Observing equipment was relocated to the Post Office Building at Central Avenue and Fillmore Street on October 22, 1936.
OCT 1953 Official observations are transferred to weather observing equipment located at Phoenix Sky Harbor Airport, near Terminal 1, on October 1, 1953.
MAY 1958 Observing equipment was relocated to the FAA Operations Building near Phoenix Sky Harbor Airport on May 29, 1958.
JAN 1978 Observing equipment was relocated to the National Weather Service office, located toward the northwest corner of Phoenix Sky Harbor Airport grounds, on January 25, 1978.
MAR 1994 The Automated Surface Observing Station (ASOS) was commissioned on March 1, 1994. The equipment is installed toward the northeast corner of Phoenix Sky Harbor Airport grounds.
OCT 2000 The ASOS equipment is relocated toward the south-central grounds of Phoenix Sky Harbor Airport.
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