Last week’s Pacific Northwest heatwave spiked temperatures in Portland, Ore. and Seattle. Both cities recorded temperatures over 100 degrees for three days straight. Temperatures hit 108 degrees in Portland on June 26, 112 degrees the next day, and 115 degrees the following day. Seattle experienced heat of 102 degrees, 104 degrees, and 107 degrees in the same period. Seattle had logged three-digit temperatures just twice before in the past 70 years. Temperatures hit 103 degrees on July 29, 2009, and 100 degrees on July 20, 1994.
Seattle is particularly vulnerable to high temperatures because most households do not have air conditioning. Portland also reports lower rates of air conditioning compared to other major cities.
Ninety one percent of American households had central air or window units in 2019, according to the Census Bureau. But of the largest 15 metro areas, Seattle had the fewest homes with air conditioning, at 44%. Around 22% of Seattle households have central air, while 15% have air conditioning in no more than one room.
Air conditioning usage varies by city and typically tracks with average summer temperatures. About 99% of households in Houston, Miami, and Atlanta had some form of air conditioning in 2019, the most of the 15 largest metro areas. June and July temperatures average almost 93 degrees in Houston and in the high 80s in Miami and Atlanta.
About 44% of Seattle households have air conditioning.
Areas like Seattle, Portland, and San Francisco average summer temperatures in the 70s and have some of the lowest percentage of homes with central air. Seattle has averaged a temperature of 73 degrees in June and July since 1948.
Air conditioning usage has increased in recent years, with usage rates rising from 89% of households in 2015 to 90% in 2017.
Weather stations used for temperature estimates: Houston Intercontinental Airport, North Miami Beach Number 2, Atlanta Hartsfield Jackson International Airport, Seattle-Tacoma International Airport, Portland International Airport, and San Francisco International Airport.