August 1967: Seattle’s Hottest Month on Record

UPDATE: July 2015 is now Seattle’s warmest month by average overall temperature, at 71.2 degrees—and August 2013 is the warmest by average low temperature, at 59.9 degrees. August 1967 remains Seattle’s warmest month on record by average high temperature (83.7 degrees).

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46 years ago, deep into the Summer of Love, hearts weren’t the only thing ablaze in Seattle.

The mercury was also on fire.

Relentless heat dogged the city during August 1967, making it the hottest month in Seattle history—an honor that has stood the test of time ever since. No matter how you score it—by average high temperature (83.7 degrees), average overall temperature (71.1 degrees) or even average low temperature* (58.4 degrees)—August of ‘67 still tops the charts all these years later.

The month began with a three-day excursion into the mid 80s, setting the tone for what would become its main calling card: persistent very warm temperatures, day in and day out— versus a major record-smashing heat wave spread out over fewer days, like July 2009.

Following the sneak preview, Seattle dropped back into the 70s for a few days before embarking on an incredible 12-day run, from Aug. 9-20, where the high temperature never fell below the mid-80s. (The normal high in Seattle in mid-August is around 77 degrees.) The mercury sprang into the 90s on three occasions during this stretch—including a sweltering 98 degrees on Aug. 16 (at the time, the hottest temperature on record at Sea-Tac Airport)—and hovered in the upper 80s most other days.

Such a prolonged stretch of consistently very warm to hot weather is pretty unusual in Seattle—generally, we’ll string together three or four days in the upper 80s or 90s before a strong marine push blows through, knocking temperatures back into the 70s. Even one of the hottest periods in Seattle history—the stretch from late July to early August 2009—fails to match up to the Summer of Love in this regard, logging 10 straight days in the mid 80s or higher to 1967’s 12. Likewise, relief arrived a little sooner following the scorching heat wave of August 1981—which set the record for consecutive days in the 90s (five straight) —with the high temperature falling into the 70s after 10 days.

Once the balminess subsided, August 1967 briefly cooled into the 70s before putting on one last simmering show. The mercury rebounded to 89 degrees on the 26th, then spiked to 95 two days later—a daily record for Aug. 28 that still stands. With this final surge, the month finished with an average high of 83.7 degrees—a whopping 7 degrees above normal. That’s well above the toasty 81.4-degree mean logged during Seattle’s second-warmest month, July 1958—and nearly 3 degrees warmer than the average high temperature in July 2009.

True, August 1967 takes a backseat to 2009 in the major heat wave department—Seattle never cobbled together more than two 90-degree days in a row then—but when it comes to continuously warm weather, day after day, the month is unquestionably second to none.

Which is why, nearly a half-century later, it remains Seattle’s hottest on record—a month that, despite the summer it belonged to, may not have received much love.