If this July ends up as the warmest month on record in Seattle, does it deserve an asterisk?
Luckily, it looks like we’ll be able to dodge this thorny issue—just barely.
Serious questions have been raised in the past week about the accuracy and siting of the temperature sensor at Sea-Tac Airport—by myself, UW Professor Cliff Mass, and former Washington state climatologist Mark Albright. To recap: On hot days this July, the sensor has been running several degrees warmer than nearby reporting stations, in addition to typically outperforming Boeing Field. This is similar to an issue that plagued the sensor during the summer of 2013 and led to a slew of suspect temperature readings—a problem that ultimately fixed itself when the sensor broke in March 2014 and was replaced. (Author’s note: The National Weather Service inspected the airport sensor on July 26 and says it is working properly.)
One of the main worries among myself and other climate watchdogs has been that the Sea-Tac numbers could inflate Seattle’s unquestionably warm July by enough of a degree to make it the hottest July—and by extent, hottest month—ever observed in the city’s period of record-keeping (which dates back to 1894). Thankfully, a pair of sub 90-degree days at the airport on Friday and Saturday, combined with a much-anticipated cool-down tomorrow, will likely keep July 2018 out of the top spot.
Below are answers to two of the most common questions we’ve received about the heat.
What month was Seattle’s warmest ever?
The warmest month ever recorded in Seattle history was July 2015, with an average temperature of 71.2 degrees. July 2015 also set the record for most 90-degree days in a month, with 10 total—including 5 straight from July 1-5 (tying July 14-18, 1941 and Aug. 7-11, 1981 for most consecutive days at or above 90 degrees).
Prior to July 2015, the champ of hot weather was August 1967—smack dab in the middle of the Summer of Love. With an average temperature of 71.1 degrees, suffice it to say hearts weren’t the only thing ablaze in Seattle that month.
What spot in the records books is July 2018 likely to claim?
Through July 29, the average monthly temperature in Seattle is 70.5 degrees. Factoring in the predicted high temperatures for later today (90s all around, alas!) and tomorrow (mid 80s, or what counts as cool this month), in addition to the overnight lows, July 2018 will likely end with an average monthly temperature of 70.9 degrees, give or take. This would make the month the second-warmest July on record (behind 2015) and Seattle’s third-warmest month overall.
The good news? Things look to return to normal as the calendar flips to August, with a steady diet of morning clouds, afternoon sun and highs only in the 70s.
In other words, the definition of pleasant by any stretch of the imagination. No asterisk needed.
