Does Seattle need AC? Western WA averaging more than double the 90-degree days it had a generation ago

The recent spell of ‘hot’ weather earlier this month and the strong likelihood of more hot weather this summer begs the question — is air conditioning (AC) now needed in western Washington?

In the 20th century, Seattle averaged about three days of 90 degrees or better. Some years did not reach 90, while others had as many as seven or eight days in the 90s. In the past 15 years, that average number has risen to eight days of 90 or better in Seattle. In 2015, there were a record dozen days of such hot temperatures.

In the 1990s, about 15% of Seattle area homes had air-conditioning. Today, that percentage has risen to around 50%. That higher number is the result of more homes being built with AC, plus others adding room AC units or replacing heating units with heat pumps that also include AC service.

Adding AC to an existing home or apartment is an expense that some cannot afford. Those without AC usually use fans to help manage the heat.

No AC? Use fans and sea breezes to your advantage

A best practice for using fans is to take advantage of prevailing wind directions during the nighttime cool-down in temperatures. During the heat of the day, keep windows closed to keep the hotter temperatures out of the home.

In the North Sound, that region can take advantage of the cooler sea breeze that often blows east through the Strait of Juan de Fuca during late afternoons, evenings, and overnight time periods.

As an example, in southern Snohomish County, after the heat of the day, open north- and south-facing windows. Place one or more fans in the north-facing windows to blow cooler air in from outside, and for the south-facing windows, place fans facing outside. This fan orientation helps draw cooler air inside and blow warmer air outside — a nice circulation to help cool things down.

For those in the South Sound, a similar sea breeze blows in from the Grays Harbor area. The fan and window orientation will often be the opposite of the North Sound, with the circulation blowing from south to north.

For those in the central Sound like Seattle, Bellevue, and Bremerton, the wind direction each night can be different. Pay close attention to the local wind forecast conditions to best determine how to orient the fans in their appropriate windows.

The latest seasonal weather outlook for western Washington points toward another warmer and drier summer. The odds are in favor of more 90-degree or better days ahead. Air conditioning is a great asset during such hot weather conditions. For those without AC, using fans and taking advantage of cooler sea breezes can help endure those periods of hot weather.

Ted Buehner is the KIRO Newsradio meteorologist. Follow him on X and Bluesky. Read more of his stories here.