How hot did it really get in Spokane on 29 June 2021?

After our historic heat wave of 2021, it's time to take a look back and answer the question of just how hot did it really get in Spokane on June 29th.  Unfortunately, the answer does get a little sticky.  First we need to look back in history, as well as look at the topography of Spokane.

Temperature measurements in Spokane started in 1881, and these were taken in downtown Spokane.  The Weather Bureau office moved out to Felts Field in 1941, and with it, the official temperature of Spokane moved as well.  Observations were still taken in downtown Spokane, they just were no longer official.  Six years later, the Weather Bureau moved again, from Felts Field to Geiger Field (which would later become Spokane International Airport) on the West Plains of Spokane.  The official observation for Spokane has been at the airport since 1947.

Moving the observation from downtown to Felts Field probably didn't have much of an effect on the temperature readings.  Both locations are at about the same elevation.  But in the 1940s, the area around Felts Field was more rural than downtown, so there may have been a little less "urban heat island" effect.  However, the move to the West Plains in 1947 was significant.  The elevation of downtown Spokane is about 1890' above sea level.  Felts Field is at the 1953 foot elevation.  But the Spokane International Airport is up at 2356 feet, an increase of nearly 500 feet.  Using the thumb rule of 5.5 degrees per 1000 feet, that results in a difference of about 2.5 to 3 degrees between the West Plains  and downtown. 

It's important to note that downtown Spokane is about the lowest elevation of the entire metro area.  57th Avenue on South Hill is at about 2360', which is the same elevation as the airport. Same goes for Five Mile.  Even I-90 at Stateline is at about 2100'.  So your location in the metro area has a big effect on your temperature, just from the standpoint of elevation.

Additionally, your surrounding environment also has an effect on your temperature.  If you're downtown with lots of concrete and asphalt, the temperature is probably a few degrees warmer than if you're near the river or at a golf course.

Late July of 1928 was extremely hot across the Inland Northwest.  Triple digits were common just about everywhere for several days.  For many locations, July 26th 1928 became the hottest day on record at the time.  Prior to this event, the hottest temperature on record at Spokane was 104F, set in 1898.  That mark was tied on July 24th and 25th of 1928, after a 102F on the 23rd.  On the 26th, temperatures peaked as Spokane hit the 108F mark.  Some other extreme readings on that day included:

• Omak  -  114F
• Ephrata  -  112F
• Lewiston  -  113F
• Orofino  -  114F
• Walla Walla  -  113F

The record of 108F for Spokane stood through for more than 3 decades of summers.  There were attempts, mind you.  The thermometer reached 106F in 1931 and 1934, and 105F in 1939.  Then in early August of 1961, extreme heat returned to the Inland Northwest.  This time the heat lasted only 3 days, but the extremes were more impressive.  Spokane once again touched 108F, tying its all-time record.  But recall that the weather observation moved up in elevation in 1947.  So which was the hottest day, 1928 or 1961?  Since downtown Spokane is typically a bit warmer than the airport, it's likely that 1961 was truly the hottest day.  And in fact, there was still a weather observation in downtown Spokane in 1961 and it reached 109F on 1961. This value was matched in Coeur d'Alene and St Maries.

Additionally, 1961 set the record for the hottest day in Washington state history, with a reading of 118F at Ice Harbor Dam (along the Snake River just east of Tri Cities).

So now we return to present day Spokane, and the 2021 historic heat wave.  We all know by now that Spokane Airport hit 109F, setting the all-time record for the city.  But was that truly the temperature that the citizens experienced?  After all, there's not many people who live at the Spokane Airport.  Thankfully, we now have a number of temperature measurements available to us to answer that question.

So while it was 109F on the West Plains, it was 113F at Felts Field.  So perhaps that should be the official temperature observation for Spokane during this heat wave?   Is that what most people experienced?  But then you notice that it there's quite a range of temperatures around the metro area.  It was 115F along I-90 in Spokane, but 108F near High Drive, and only 106F in Opportunity/Spokane Valley.  So perhaps the 109F at the Spokane Airport is a decent "middle of the road" temperature for the area.

For a bit broader view, several locations set their all-time high temperature record in the Inland Northwest on June 28th.

• Omak: 117F, old record 114F (26 Jul 1928)
• Wenatchee: 113F, old record 110F (18 Jul 1941)
• Bonners Ferry: 108F, old record 105F (11 Aug 2018)
• Chelan: 111F, old record 110F (29 Jun 2015)
• Davenport: 107F, old record 105F (26 Jul 1928)
• Mazama: 112F, old record 103F (1 Aug 2020)
• Northport: 113F, old record 110F (28 Jul 1934)
• Odessa: 115F, old record 112F (4 Aug 1961)
• Plain: 109F, old record 104F (27 Jul 1939)
• Priest River: 108F, old record 105F (10 Aug 2018)
• Republic: 109F, old record 108F (2 Jul 1924)
• Rosalia: 111F, old record 108F (27 Jul 1934)
• Sandpoint: 106F, old record 104F (24 Jul 1994)
• Wilbur: 110F, old record 110F (3 Jul 1922)

But not every location set all-time records.  Coeur d'Alene hit 108F for 2 consecutive days in this heat wave, but both fell short of their all-time record of 109F in 1961).  A similar story for Grand Coulee Dam.  Moscow and Pullman fell 4 degrees short of their 1961 record.  

Daytime high temperatures weren't the only records broken.  The nighttime temperatures were rather uncomfortable as well.  Spokane airport also set an all-time record for warmest low temperature.  It tied the record on the morning of the 29th, cooling only to 77F.  This equaled the record set back on 27 July 1928.  After topping out at 109F during that afternoon, the temperature was only able to cool to 78F by the morning of the 30th, setting the all-time record.

The all-time high temperature record for Washington of 118F may have been tied or even broken at a few different locations during this recent heat wave.  A climate extremes committee will review this in the coming months.