Wildfire smoke dampens high temperatures by day, traps heat overnight

Oregon’s wildfire smoke is keeping its sizzling temperatures from soaring even higher during the day, but that smoke is also trapping overnight heat.

Wildfires are burning from western Canada down to Northern California, engulfing major parts of the West with wildfire smoke. This prompted the Oregon Department of Environmental Quality to issue and extend an air quality advisory on Friday for several parts of the state.

The agency expects the air quality advisory to stay in place through at least noon Monday. Air quality is considered unhealthy in most parts of Oregon, and with a continuing heat wave, it’s also creating ozone pollution or smog in some areas like Portland.

“That often happens when extreme heat and sunlight are low to the ground and there are no winds,” DEQ Public Affairs Specialist Susan Mills said. “So we end up getting haze and smog and this tends to be more active in the late afternoon and early evening when a lot of people are driving home from work, when there tends to be more cars on the road.”

Related: Heat wave puts Oregon’s new worker protection rules to the test

Portland State University associate professor of geography Paul Loikith said it’s a fairly common combination when the region experiences extreme heat and smoke. He said the stagnate wind pattern is what is creating more problems.

“There’s really nothing to make that smoke get out of the region or to be transported off to the east and away from the Pacific Northwest,” Loikith said. “There’s not a lot either to mix the smoke vertically with cleaner air from aloft. It just kind of sits near the surface and drifts around and accumulates.”

Loikith said although the smog is creating some relief from the heat during the day, with no winds to push it out, that means there will be higher overnight temperatures.

“It can kind of narrow that range from the daytime to nighttime temperature with taking the edge off the daytime heat but keeping nighttime temperatures a little bit elevated,” he said.

The agency recommends people keep an eye on the Air Quality Index, as the levels of smoke and smog can change and could create pockets of clearer air. Smoke and smog can cause irritation to the eyes and lungs and contribute to breathing problems. People should stay inside, avoid being outdoors and use a HEPA air filter if possible. DEQ also recommends wearing an N95 mask if going outdoors, as cloth and surgical masks do not provide the same protection from the smoke and smog particles.

Loikith said cooler weather is still a few weeks away for the region.

“Triple digit heat has occurred into the beginning of September and then 90 degree plus heat has happened well into September,” he said. “But we do tend to lose the ability to get really, really hot by about mid- to later September and it happens pretty quickly.”

Meanwhile, Oregon Occupational Safety and Health Division, which goes by Oregon OSHA, and several partners will be distributing hundreds of thousands of N95 and KN95 masks to protect workers under the new temporary rules adopted last week. The rule requires employers to provide N95 masks when the air quality exceeds more than 101 on the Air Quality Index. Employers will also be required to reduce exposure to wildfire smoke if the AQI reaches more than 201.

Oregon OSHA, working with the Oregon Homebuilders Association, the Associated General Contractors Oregon-Columbia Chapter, and Hoffman Construction, will be creating distribution sites to give out the free masks. Oregon OSHA will also be coordinating with the Oregon Department of Agriculture on the distribution of the masks to agricultural workers.