Tuesday, July 16 is shaping up to be a hot one across the Puget Sound region, with temperatures climbing into the upper 80s and low 90s (around 31–33 °C). But despite the rise in heat, meteorologists are clear: this is not a historic heat wave.
“It’s going to be warming up a lot from yesterday,” said Cliff Mass, professor of Atmospheric Sciences at the University of Washington, during an appearance on The Jason Rantz Show on KTTH. “It’s not the end of the world. We’re looking at mid-80s in many areas. Yesterday was cooler, but now things are heating up fast.”
Most of the lowland areas south of Seattle are expected to reach the mid-80s (around 29 °C), while northern parts of the region will stay a bit cooler. By Wednesday, highs near or just above 90 °F (32 °C) are likely across the Seattle metro area, with slightly hotter conditions to the south.
“Wednesday will clearly be the hottest day of the week,” Mass said. “Then by Thursday, marine air starts to move in. We’ll see a drop of at least five degrees, and by the weekend, we’re back in the 70s.”
A warm stretch—but not historic
Mass pushed back on any notion that this week’s weather qualifies as a major heat event. “If you’re calling this a historic heat wave, that’s simply not the case,” he said. “It’s a warm spell, definitely above average for this time of year. But remember—normal highs for mid-July in Seattle are around 80 °F (27 °C). This is typically the warmest, driest time of the year, so it’s not unusual to get this kind of stretch.”
Cooler air, better air quality
With onshore winds expected later this week, a shift to cooler, more moderate conditions is on the way. Still, daytime highs should remain slightly above average, hovering in the mid to upper 80s (around 29–31 °C) until the weekend.
Air quality, often a concern during summer heat events, has remained strong. “In fact, fire activity has been well below average this year,” Mass added. “Despite all the talk of dry weather, we’ve had very little smoke and few fire concerns west of the mountains.”
Summer nights getting warmer
Meanwhile, new data from Axios Seattle highlights a long-term trend: summer nighttime temperatures have risen significantly across the Pacific Northwest. From 1970 to 2024, 96% of U.S. cities studied saw nighttime summer lows increase. In Seattle, the average summer low has risen by 2.9 °F (1.6 °C); in Yakima, by 4.3 °F (2.4 °C); and in Spokane, by 5.1 °F (2.8 °C).
Mass noted that while nighttime temperatures are rising, it’s important to consider why. “People care about daytime highs, but those haven’t gone up nearly as much,” he explained. “Nighttime temperatures are more sensitive to the urban heat island effect, where concrete and buildings trap heat, keeping city temperatures higher overnight.”
So while Puget Sound bakes under above-normal warmth this week, the broader context shows it’s nothing out of the ordinary—at least for mid-July in Western Washington.
