Seattle has officially tied the longest streak of rain-free weather at 51 days.
At 12:01 a.m. Wednesday, we broke that record. With a few showers finally returning to the forecast by Sunday and Monday of next week we'll probably end the streak at 56 or 57 days.
The previous record was set in 1951.
The rain gauge at Sea-Tac has not measured rain since June 17. However, rain gauges north and south of Sea-Tac recorded measurable rain on July 20, breaking the dry streak in other parts of Western Washington.
Measurable rain is .01 inch or more.
This has always been the driest time of the year. When you add up the "normal" rainfall from June 18 through Tuesday you only get 1.35 inches, so really we're not that far below average. In fact, even with this current dry streak, when you add up all the rainfall so far this year we're still over 8 inches above the normal yearly rainfall total to date.
The dry streak record is coming off the heels of one of the wettest stretches Sea-Tac has recorded. Seattle accumulated 47.24 inches of rain between October 2016 through May 2017, making it the wettest fall, winter, and spring on record. Just the three months from the start of February through April that same Sea-Tac rain gauge recorded rain of 20.4 inches.
Between January and the end of May, 70 percent of days in Seattle had rain.
Other recent weather records:
- Completely dry July: Never (we measured just a trace)
- Measuring only a trace of rain in July: 4 (2017, 2013, 1960, 1958)
- Days hitting 70 or warmer: 62 (currently at 41)
- Days hitting 80 or warmer: 15 (currently at 11)
Compared to other parts of the country, and even our nearest major city, this streak is somewhat measly. The record dry streak for Minneapolis is 51 days, Portland is 71, Phoenix is 143, and the driest place, Death Valley, has actually had two separate YEARS when no rain fell (1929 and 1953).
Are polar opposite records set nearly back to back in the same year anything more than a curiosity? Maybe. But they fit in with broader trends says University of Washington atmospheric scientist and state climatologist Nick Bond.
“The big years are bigger than they used to be,” said Bond, pointing to several graphs of western Washington weather data dating back to the late 1890s, including one on rainfall.
And needless to say not all that data was recorded at Sea-Tac, which came into being during World War II. In those same charts, average nighttime temperatures have gone up from close to 50 degrees Fahrenheit to nearly 55 degrees. Three of the strongest spring rain years have happened in the last five.
“Our trend is toward wetter springs and toward warmer summers,” said Bond. “The trends are unmistakable.”
That’s particularly in regard to nighttime temperature, which tend to dampen out wider swings recorded in the daytime hours.
For wildland firefighters, that wet late spring was bad news, creating bumper crops of grasses and other light fuels, now well cured.
Ironically, the fire danger in Washington state is slightly lower because of a blanket of wildfire smoke hanging over the state. Smoke coming from huge fires in British Columbia. Temperatures lowered slightly, because the blanket is thick enough limit enough sun to make temperatures in Washington a few degrees cooler, and heat is a major driver of wildfires.
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