Washington has a new record high temperature

SPOKANE, Wash. — It got so hot last summer, it officially broke the record for the hottest temperature in Washington State.

Located just northwest of Tri-Cities, Hanford hit 120°F on June 29, 2021. That’s the highest temperature the state has ever recorded.

And it’s not just Hanford, as dozens of cities and towns in the Northwest hit their highest temperatures on record last summer during a historic June heatwave. Spokane, Seattle, and many cities in Oregon broke their previous records on that same day. The state temperature record of 119°F in Oregon was tied in two locations in the northern part of the state.

Spokane hit 109°F on June 29 as well, the highest the city’s ever seen in 140 years of records.

The National Weather Service confirmed on Thursday the new temperature records for both states. Between July and December 2021 a committee of meteorologists and climatologists painstakingly analyzed the 31 weather stations that broke the old state record of 118°F. This record has happened twice, one in 1928 and the other in 1961.

Wx Heat

Locations where weather stations reported readings over the old WA state record of 118 degrees. Each station needed to be verified during the autumn of 2021.

According to the committee report, stations from the Washington Department of Ecology were thrown out of the running because of a “warm bias” in their design. As the report explained, not all weather stations around Washington have weather collection as their primary objective. A collection of other instruments on these WDOE stations is set directly below the temperature sensor with a heat vent on top of the housing. This means warm air heated inside in the metal housing could rise directly into the temperature sensor and give a biased reading that doesn’t reflect the actual air temperature. Satellite temperature measurements further confirmed that these stations, mainly around the Blue Mountains, were giving readings (up to 134°F) that were too suspicious to be believed.

Hanford Station

Hanford weather station that set the new WA state temperature record. Source: NOAA

The next warmest sensor during the June heatwave is part of a network of weather stations that monitors the Hanford Site north of the Tri-Cities. The original hottest temperature record in Washington of 118°F from 1928 happened across the river from the Hanford Site in Wahluke. Satellite measurements and temperatures from nearby National Weather Service sensors gave lots of circumstantial evidence to support the Hanford reading.

Old V New Heat

An investigation of the weather station site could not find any biases and further analysis backed up the reliability of the station. The committee found that a southerly downslope wind across the Hanford Site shortly after 6 p.m. on June 29th helped warm the air just enough to set the new hottest temperature in Washington State history.

Despite the Hanford station sampling temperature slightly differently than NWS stations, the committee voted unanimously to certify the new record of 120°F.

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