Wildfire smoke is expected to creep back into Portland air after 11 p.m. on Sunday, according to the National Weather Service.

From there, it gets worse.

The National Weather Service predicts widespread smoke Monday as well as Tuesday with temperatures in the 90s.

Smoky skies are expected last through Wednesday, according to a release by the Oregon Department of Environmental Quality.

Just how bad the air will get remains unknown.

The Oregon Department of Environmental Quality and Southwest Clean Air Agency have issued an air pollution advisory that covers parts of Portland much of the Willamette Valley.

The Pacific Northwest has been engulfed in smoke this summer due to wildfires. On some particularly smoke-filled days schools have shut down outdoor activities. At one point this summer, Portland's air quality ranked among the worst in the world, placing fourth behind cities such as Mumbai, India, and Dubai in the United Arab Emirates.

The Department of Environmental Quality suggests the following precautions:

- Be aware of smoke concentrations in your area and avoid the places with highest concentrations.

- Avoid strenuous outdoor activity in smoky conditions.

- If you have heart disease, asthma or other respiratory ailments, or are over 65, you have a higher risk of illness from wildfire smoke.

- Small children and pregnant women are also at increased risk. These residents are encouraged to stay indoors.

- People suffering from asthma or other respiratory problems should follow their breathing management plans or contact their healthcare providers.