The Tri-Cities Airport observed its first 100 degree reading Wednesday afternoon thanks to this early June heatwave, leading to a new record. The preliminary high temperature was 104°, beating the old record of 103° set in 1986. A heat advisory remains in effect for the Columbia Basin until 20:00 Thursday with upper 90s likely for one more day.
RECORD HIGHS WEDNESDAY
| City | High | Old record (year) |
| Hermiston | 102 (tie) | 102 (1937) |
| Pendleton | 100 | 96 (1913) |
| Tri-Cities | 104 | 103 (1986) |
| Walla Walla | 99 | 98 (1970) |
| Yakima | 100 | 95 (2007) |
The axis of the upper level ridge producing the high temperatures will be moving eastward beginning Thursday. This will turn upper level winds to being out of the southwest, injecting some moisture and energy into the atmosphere. A chance of thunderstorms exists generally east of a line from Bend to Hermiston to Dayton with a marginal risk (level 1 out of 5) of severe thunderstorms over the Blue and Wallowa Mountains. While a shower may stray into the Columbia Basin, low dew points and hot temperatures will likely combine to keep storms away from the Tri-Cities.
With the weather pattern moving out, winds are likely to increase during the day Friday. Despite high temperatures dropping down to the upper 80s Friday afternoon, relative humidity values may be below 10% in some spots. Conditions that dry with strong winds will be ideal for rapid fire growth, prompting the National Weather Service to issue a fire weather watch from 11:00 to 22:00 Friday.
Temperatures continue to cool into the weekend under the influence of a broad upper level trough. By Saturday, most locations around the Columbia Basin should see highs in the 70s. Westerly flow aloft is expected to contribute to breezy conditions both Saturday and Sunday. Fortunately, cooler temperatures will make the fire weather situation far less dangerous. Still with dry vegetation, it’s important to be careful when dealing with something that could start a fire.
Current indications are that highs in the 70s may stick around as long as Tuesday with locally breezy conditions through Wednesday in typical windy spots. Upper level winds turning out of the southwest again will probably facilitate another warming trend midweek with highs returning to the 80s Wednesday.
Data in this post is accurate as of 17:45 PDT Wednesday.
