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PROSSER, Wash.- Only three words are needed to describe this summer in Washington state: hot, hotter and hottest.

In Prosser, August ended with the hottest temperature since 1991, and the June to August period was the second warmest on record.

“Low temperatures in August were the warmest on record as a result of last month’s humid and periodically cloudy conditions,” AgWeatherNet Meteorologist Nic Loyd said. “In a broader context, however, this summer is just the latest noteworthy episode in a continuing warm period that has persisted in central Washington for a year and a half.”

Warming up

Summer 2013 marks the sixth consecutive season of warmer than average temperatures, while August represents the thirteenth of the last 14 months to feature above normal temperatures. The 2.1 degree rise above normal summer temperatures makes this the most significantly above-normal season in more than a decade.

“Despite this summer’s abnormal conditions, crops were generally faring well as we progress into the harvest season,” said AgWeatherNet Director Gerrit Hoogenboom. “Fortunately, most of the weather-related agricultural problems have been isolated in nature. One example is the thunderstorm-induced hail and wind damage that occurred on fruit trees north of Wenatchee on August 10th.” 

June was a relatively warm month, despite several rain-cooled days in eastern parts of the state. However, hot and dry conditions during July set numerous records. Mt. Vernon experienced only its second rain-free month on record, while Prosser recorded its warmest monthly mean high temperature on record of over 92 degrees. The heat wave of July 1-2 brought not only the hottest temperatures to the region in four years, but also the earliest major hot spell since 1992. Temperatures peaked at 108 degrees at Benton City, while low temperatures as warm as 81 degrees were recorded.

Stormy weather

August actually began with relatively cool and unsettled weather. The rain-cooled high temperature was only 59 degrees at Green Bluff (near Spokane) on Aug. 2. Temperatures quickly rebounded, however, and Hundred Circles (west of Paterson) reached 100 degrees just four days later on Aug. 6. Most of the month was hot and somewhat humid, as periodic impulses spawned several episodes of thunderstorms.

On Aug. 1, a storm dropped a torrential downpour of 0.63 inches at East Wenatchee, despite the fact that nearby locations received almost no rainfall. This theme of occasional bouts of brief and isolated heavy rain events continued through the month. On Aug. 10, another deluge brought 0.79 inches of rain to WSU Sunrise Research Orchard in just 15 minutes. One of the few cool temperatures of the month occurred on Aug. 21, as Pullman dropped to a chilly low of 37 degrees. However, heat and humidity returned quickly. As the summer came to a close, western Washington finally received their first widespread rainfall in two months on Aug. 28 and 29. A much-needed 0.89-inch rainfall occurred at Poulsbo South on Aug. 29. 

Unfortunately, numerous fires were an undesired consequence of the scorching summer weather, although smoke concentrations never approached the dangerous levels observed in 2012. Other summer weather highlights include a 0.75-inch rainfall at Prosser on June 18, and a daily high of only 49 degrees at Green Bluff on June 20.