Plenty of sun — and smog

Summer announced itself this week with plenty of sun, record high temperatures, great beach weather — and more smog.

With heat and limited air movement trapping pollutants, the National Weather Service issued an air-stagnation advisory in effect until 5 p.m. today. Heat advisories also were issued across large parts of Washington, with temperatures in Spokane and other inland areas hovering in the mid-90s.

Monday's record high temperature of 90 in Seattle and highs of 94 in Bellevue and 83 in Everett marked the expected peak of a warming trend in the area that began with last Friday's high of 74 degrees in Seattle. The previous Seattle record for the date, 88 degrees, was set in 1987.

Daytime temperatures are expected to fall to the upper 70s by the weekend, but it still will be warmer than the seasonal average of 72.

Though temperatures above 90 are uncommon in this area, "a warm spell in late June is certainly not unusual," said Dustin Guy, a National Weather Service meteorologist. The average seasonal high of 72 is based on 30 years of thermometer readings, and variance from year to year is normal.

And smog has been gathering as temperatures have risen, said Mike Schultz, a Puget Sound Clean Air Agency spokesman. Chemicals in car exhaust react with heat and sunlight to produce ozone and other components of smog.

Emissions from Seattle's urban corridor usually float east and southeast, carried by the wind, becoming smog by the time they settle over foothill communities such as North Bend and Enumclaw. Air quality gets worse as the day goes on. "Though the higher levels are reached in these foothill communities, I think it's important for people to realize we're in this together," Schultz said.

While air quality suffers in the heat, the region's water supply is in good shape. Regular precipitation and above-average snowpack in recent months filled the reservoirs by early June.

Though city officials encourage residents to be mindful of their usage, "we've got every indication we've got enough water for the summer," said Dave Hilmoe, drinking-water director for Seattle Public Utilities.

Charlotte Hsu: 206-464-8349 or chsu@seattletimes.com