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Washington state's new maximum temperature record: 120 degrees Fahrenheit

After a months-long investigation, the State Climate Extremes Committee accepted a 120° reading taken at the Hanford site as the state's new maximum temperature.

Editor's note: The above video about the long-term heatwave outlook for Washington state originally aired June 28, 2021.

RICHLAND, Wash. - Eight months after the fact, Washington state officially has a new maximum temperature record: 120 degrees Fahrenheit. 

The reading was taken by the Department of Energy at the Hanford Nuclear Reservation on June 29, 2021, during a historic heatwave in the Pacific Northwest.

The previous record of 118 degrees Fahrenheit was set in Wahluke, Wash., on July 24, 1918. 

Although the reading was taken over eight months ago, the State Climate Extremes Committee completed an investigation before accepting the record-breaking temperature observations taken that day. 

There were over two dozen readings taken on June 29, 2021 that registered temperatures that matched or exceeded the previous maximum temperature record for Washington state. However, the SCEC deemed many of the reports "unsuitable for further consideration" for a myriad of reasons. 

Some instruments were used for purposes other than meteorological accuracy and some were taken by commercial or privately owned networks, which likely did not match up to SCEC standards, according to a report.

Nearly a dozen readings taken by the Washington State Department of Ecology that registered above the 118-degree record -- with some going as high as 134 degrees -- were dismissed. The report said the instruments used were intended to monitor environmental quality and were located above metal instrument housing causing the readings to come out too extreme to be considered valid. 

The committee cross-referenced the remaining temperature readings with infrared imagery from several polar-orbiting satellites to confirm the readings were taken in the same areas where the hottest surface temperatures were observed, according to the report. 

One image clearly showed the hottest temperatures in Washington occurred in the area of the Hanford Nuclear Reservation. 

Credit: Courtesy of the State Climate Extremes Committee
An infrared image of Washington state taken on June 29, 2021, shows the hottest temperatures were occurring around the Hanford Nuclear Reservation, which recorded a new Maximum Temperature record for the state at 120 degrees Fahrenheit.

Temperature readings around the reservation area and readings taken by Washington State Department of Transportation instruments within the reservation recorded similar temperatures around 118 and 119 degrees Fahrenheit. 

The previous maximum temperature record for Washington was set on July 24, 1918, at a National Weather Service Cooperative station in Grant County along the Columbia River, according to the report. The record was matched at the Ice Harbor Dam on Aug. 5, 1961. Before that, the maximum temperature record of 115 degrees Fahrenheit was taken in Kennewick in 1898.

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