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July 2015

June Boon

Posted: July 2nd, 2015


In the red


Generations of Seattle-area residents have been acclimatized to expect a persistently warm and dry summer that begins after Independence Day. This year is different: cases could be made that the season began June 4 or even May 15. Those dates represent our last two bouts of solid onshore flow, also known at this time of the year as “June Gloom.”


It is safe to say that at this moment, almost all Seattle residents would welcome, say, 75 degrees for a high temperature. But for another week that mark would still be above normal. The fact that our definition of relief has changed is a sign that we’ve at least temporarily adapted to a climate change. If ‘weather is what we get, and climate is what we expect,’ it might be said that our expectations have fundamentally changed.


June 2015 was by far the warmest June on record in Seattle. At 67.7 degrees it was warmer than a normal July and August, too. June’s average high temperature was 78.9 degrees, which is a full 3 degrees warmer than the previous record set in 1992. Five out of the last nine months have set all-time warmest records. And June was also our 16th consecutive warmer-than-normal month overall.


With a record 13 days at 80 degrees or warmer, all but one high temperature since the 4th of June was above normal—all but 9 since 5/15. Somewhat oddly, only two of those highs tied daily records (87 degrees on 6/8, 92 degrees on 6/27). And only one morning low temperature was below normal (43 degrees on 6/7).


Perhaps the geekiest statistic of June 2015, which was noted by KOMO’s Scott Sistek and verified by the National Weather Service, may relate to the future of heat in the Northwest: the daily record tying high temperature of 92 degrees on 6/27 was Seattle’s highest-ever reading without an East wind. We haven’t even had a classic off-shore heat wave yet this season; it has simply not been cooling off at night.


With respect to rainfall, it was our 4th driest June on record. 0.58″ fell at Seatac, but unlike most Junes when on-shore drizzle is spread out evenly over the course of the month, it only came in two bursts for a total of 4 days of measurable precipitation. Since May, we’ve only had a total of 8 official days of rain, which is the fewest on record for that period. That’s, of course, great news for SPU’s water quality and storm water managers, and a challenge for reservoir and water supply “superheroes.”


Outlooks confidently suggest continued warmth through the rest of this summer and beyond, but our current water supply outlook remains good. However, the unusual weather since May has caused inflows into our reservoirs to be quite low for this time of year; water use is also up significantly compared to typical amounts over the same period. SPU is monitoring the situation closely and carefully.


The cause for all of this heat, by the way, is most likely “The Blob” [in conjunction with high pressure]. Initially the product of an extreme atmospheric circulation pattern that occurred nearly two whole years ago—recall “Fogmageddon“—the Alaska-sized pool of anomalously warm water off our coast has more or less persisted and interacted with other warmer-than-normal regions of the Pacific to keep our normally cool on-shore flow warmer and more humid.


Pictured above as a reddish blob, the phenomenon was first identified by Washington State Climatologist, Nick Bond. It does not look like it will quit anytime soon, and as you might expect it’s now an active area of research. While the extent to which The Blob is either related to or exacerbated by global warming is unknown, its effects are consistent with heat wave and precipitation research that guides climate adaptation work at Seattle Public Utilities.