High pressure will remain in place over the region through Friday. This coupled with southerly flow thanks to a deepening low in the Pacific will amplify already hot temperatures in the Inland Northwest, prompting the National Weather Service to issue an excessive heat warning for the Tri-Cities and surrounding areas. This warning goes into effect 8 am Wednesday and lasts until 8 pm Friday. When it goes into effect, this warning will replace the heat advisory that is currently in effect. Some of these high temperatures may break daily records.
Highs over 100° are expected to last through the work week, but will peak on Thursday. On that day, highs will be near 110° in the Tri-Cities, Walla Walla, and Hermiston, with Pendleton being a few degrees cooler. Highs should remain above 105° in the lowlands on Friday. Overnight temperatures will offer some relief, but won’t drop as far as we are used to. Both Thursday and Friday morning, lows are only expected to get down to the low-70s.
Beyond Friday, an upper level trough should approach the Washington and British Columbia coasts. With it will be cooler temperatures. On Saturday and Sunday, the Tri-Cities should only reach into the mid-90s.
FIRE DANGER
Hot temperatures aren’t the only issue the Inland Northwest will have to contend with for the second half of the work week. There is a low chance of dry thunderstorms for the duration of the excessive heat warning. On Wednesday, this risk is primarily in Central Oregon, but shifts northeast into the Columbia Basin on Thursday.
Flow from the south will bring in enough moisture to initiate thunderstorm development, but hot temperatures and low relative humidity at the ground will limit how much rain reaches the surface. Rain doesn’t need to reach the ground to produce lightning, so the main concern here is that lightning will strike where rain is light (or isn’t happening at all) and spark a fire. Even dry thunderstorms can produce gusty winds, so fires that do start as a result of a lightning strike stand poised to spread quickly.
With things being so hot, it will be easy for fires to start through other means. It would be wise to limit outdoor burning during this period. Keep fire safety in the back of your mind, including not throwing cigarettes on the ground and making sure tow chains don’t drag. Last year’s big fire that scorched Rattlesnake Mountain started as a result of a tow chain dragging on Highway 24 just west of the Yakima Barricade of the Hanford Site.
HEAT SAFETY
These temperatures certainly aren’t unprecedented for our region this time of year, but still need to be taken seriously. According to the National Weather Service, heat is the number one cause of weather related deaths in the United States, beating out other extreme events like tornadoes and hurricanes. To learn about symptoms to look for, head over to this link from the CDC. Remember that heat stroke is a deadly medical emergency and warrants a call to 911. Symptoms for that include (but aren’t limited to) hot, dry skin and the victim losing consciousness.
Be sure to drink plenty of water and be alert of symptoms in yourself and those around you. As my dad likes to say – the best place to store water is in your body. The elderly, children, and those without air conditioning are particularly susceptible. Don’t be afraid to ask someone if they are okay – you could save a life!
TRI-CITIES HEAT STATISTICS
Not everyone will see temperatures reach 110° this week, but it isn’t outside the realm of possibilities for hotter locations in the Columbia Basin. One of these is the Tri-Cities Airport in Pasco, which is where official climate records for the Tri-Cities are taken. Temperatures this high are pretty rare. The last time the Tri-Cities reached 110° was in 2015, when the Temperature at the airport hit 111° on both June 27 and 28. Since weather records began in the Tri-Cities in 1894, the temperature has only reached 110° a grand total of 20 times. Only three of these days, the two from 2015 and one in 2006, have happened since 2000.
The average hottest temperature we will reach in any given year is 105°, with two thirds of years peaking between 103° and 107°. The following is a chart showing our climatological chance of reaching select temperatures in any given year. I decided to include both the current 30-year climate period (1981-2010) as well as the entire period of record (1894-2019, omitting a three year gap in record keeping).
The Tri-Cities stands a chance of breaking daily high temperature records on both Thursday (record 107°, forecast 110°) and Friday (record 108°, forecast 108°). It isn’t likely that the all-time record of 115° (set July 28, 1939) will be broken. It also isn’t likely that the Washington or Oregon state record high will be broken. Washington’s state record high is 118° set at Wahluke (near Vernita Bridge) in 1928 and Ice Harbor Dam in 1961. For Oregon, that value is 119° in both Pendleton and Prineville in 1898. Oregon’s record is disputed, however, and it’s possible the true record is 117° set at Umatilla.
Also unusual about this heat wave is how long it is expected to last. The Tri-Cities Airport reached above 105° on Tuesday. If it does this again on Wednesday, Thursday, and Friday, it will tie for the third longest stretch of consecutive days with highs at or above 105°. This is no small feat – the last time the Tri-Cities experienced four or more consecutive days at or above 105° was in July of 1979. The record currently stands at six, set in 1911, and it is extremely unlikely that this heat wave will break it thanks to the trough that is expected to reach into the state on Saturday.
Whether we break records or not, it will still be hot. Be sure to head over to Tri-Cities Weather on Facebook as well as my personal Twitter feed for continued updates!
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