hot records

7pm Tuesday…

Yesterday we hit 90 in Portland, and of course it’s been much cooler today. That was our 8th day at/above 90 this summer so far. Looks like we’ll end up close to normal this year since I see three more 90+ days by next Monday. By the way, the last cool summer? Way back in 2012.

Yesterday also happens to be one of the three times we’ve hit our all-time high in Portland…107 degrees. It happened TWICE during the big 1981 heat wave

and previously in July 1965

The all-time high at Salem and Eugene is 108, and 109 in Roseburg. I remember back in 2009…as we approached that big heat wave in late July I wondered if we were finally going to break Portland’s record. Instead we hit 106 for two consecutive days…a close call!

Wondering what the all-time record high is in Oregon? Most likely it has happened in one of three spots. The three hottest parts of our state are: Rogue Valley and surrounding low elevations in SW Oregon, the lower Columbia Basin in north/northeast Oregon, and the Snake River area right along the Idaho border. Some stations in these areas see an average July day at 90 degrees or a bit higher. You can see these areas (circled) on a PRISM map showing average July high temperatures in the region

AVERAGE JULY HIGH TEMPERATURE

Official records show both Pendleton and Prineville hit 119 degrees during a heat wave in late July and early August 1898.

But there has been some meteorological debate over at least one of those numbers. I remember the head of Portland NWS, around 1991 when I started my career, cast doubt on the Prineville reading.

  1. I don’t doubt the Pendleton number much, since that area has seen 114 (July 1928) and 115 (August 1961) during the 122 year span following the record.
  2. It’s unlikely Prineville ever hit 119, Why? In the 122 years since that time, Prineville has only been above 105 on four days! 106 in 1915/1922 and 107 in 1998. Nothing even close to that 119 degree reading, while other stations (like Pendleton) have made it to within a few degrees of their all-time records. For example, during the 1928 and 1961 heatwave (when Pendleton made it to 114/115), Prineville only hit 102. Suspicious for sure. Something strange was going on with the readings in 1898 at Prineville IMHO.

The other numbers seem reasonable; Umatilla is right at the lowest elevation along the Columbia River. Pelton Dam is down in a hot canyon location in north-central Oregon near Warm Springs. Pilot Rock is just south of Pendleton. Monument and Spray are both along the John Day River, near or below the 2,000′ elevation.  Monument has hit 116 in two different years and Spray was 1961, not 1928 (bad graphic). Beyond these numbers, there are a few places that have hit 115 including: Medford, Arlington, Hermiston, & The Dalles. Keep in mind there were not many weather reporting stations during the 1898 heat wave. In fact before that time there were very few reliable weather records. Umatilla stopped reporting in 1965. Weather records are always a challenge…

Looking ahead, we have this summer’s 2nd heat wave on the horizon; it looks very similar to what we just experienced in late July. A hot ridge of high pressure pops up over the Western USA late Friday through early next week. Models, lead by the ECMWF, are pushing 850mb temps up around +23 to +25 (Celsius) overhead along with some easterly flow over the Cascades and through the Gorge. That’s for Saturday afternoon through Sunday. That’s a recipe for 100 degrees again; or we’re going to be close! Right now our forecast looks like this

We’ll up that to 100 degrees Sunday if models look the same tomorrow. The good news is that extreme heat becomes uncommon after mid-August. So this may be our last heat wave of the season. Weakening sun energy + lower angle + longer nights/shorter days start to take a toll in late August.

Enjoy the cool nights and comfortable days through Friday!

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