It’s quite astonishing when you consider some of the meteorological records Seattle has broken this summer. Seattle set a new all-time dry streak record of 55 straight days (no measurable rainfall ≥0.01 inches), all-time record for consecutive days with highs above 70°F of 64 days (and counting!), and record for second longest consecutive stretch with highs above 80°F of 12 days.

Plenty of days had highs above 90°F, and some nearby cities (e.g. Portland) had several days above 100°F! Of course, if you are from the Southwest (dry heat) or some place often muggy, the Pacific Northwest’s heat records may not be all that impressive to you. However, the lack of rain is truly remarkable. There was zero rainfall in July, and there has been, so far, really only one day (8/13) with measurable rainfall since the middle of June! According to the U.S. Drought Monitor, most of the Pacific Northwest has been “abnormally dry” (yellow), which is comparable or worse than some traditionally dry places like Southern California or Arizona.

So what caused this persistent heat and dryness? It might be tempting to blame climate change, but, in general, the increase in average temperatures over the past decades is considerably smaller than the deviation from average this summer, so I would say that variability is more significant. Seattle is climatically quite warm and dry during the summer, and there have been many summers like this one. That said, in terms of temperature, this summer could be seen as a preview for summers in the Pacific Northwest later this century. University of Washington Professor Cliff Mass discusses human-forced climate change in the Pacific Northwest in great detail.

Specifically, many of the heat waves the Puget Sound area experienced this summer were the result of the classic offshore flow scenario. Ridges of high pressure helped keep us dry, and we occasionally got thermal troughs, which ushered in warm air from the south. The high pressure inland, frequently over the Rocky Mountains states, allows for warm air to move toward low pressure. The following surface analysis map is an example of this:

In addition, much of the Puget Sound area experienced weeks of smoke from Canadian wildfires. Essentially, during July and August, there were no particularly strong onshore winds from the Pacific Ocean or any rain, which allowed the smoke to stick around for a long time.

The air quality was very poor at times, even worse than Beijing’s air quality. Nonetheless, the thick haze produced some positive effects, such as reduced heat wave temperatures and captivating red sunrises and sunsets. In the photo to the right, one can usually see the Seattle skyline on a clear day, but the smoke obstructed the view.

To no surprise, there were excessive heat watches and warning issued throughout the summer, and the National Weather Service’s terms “areas smoke” and “sunny” became repetitive in weather forecasts.

Next week, the Puget Sound region will experience mid to upper 80s, or even 90s, with no real rain in sight yet. Although summer is technically not over yet, students across the country are resuming school or preparing to resume school. In Pennsylvania, a series of thunderstorms marked the end of the hot and humid period and the beginning of cooler, fall-like weather. For your entertainment, here is a video I took on August 19 when a line of severe thunderstorms passed over State College:

Thunderstorm over State College (8/19/17)

Now for a brief recount of the recent eclipse. On August 21 (first day of classes at Penn State), a rare total solar eclipse was observed across the United States. However, in State College, we could only see a partial eclipse (~80%). I decided to just borrow other people’s eclipse glasses to get a glimpse of it. It was cloudy and showery for a while, but just before the maximum eclipse, the sun emerged out of the clouds! I hope to witness totality sometime in my life, hopefully during the 2024 eclipse. If you have a interesting story about your experience during the eclipse or any good photos, feel free to share below!