PORTLAND, Ore. — Temperatures are expected to reach up to 94 degrees Fahrenheit (34 Celsius) in Portland, Oregon, on Saturday as an excessive heat warning is set to expire in the evening.

Cooling centers in Multnomah County, Oregon’s largest county and home to Portland, will remain open until Sunday morning for people seeking a place to escape the heat.

Although temperatures are expected to gradually cool over the weekend, officials urge residents to “practice caution” by monitoring themselves for heat illness and having access to cool spaces throughout the day.

“Several days of high temperatures stresses our bodies,” said Dr. Jennifer Vines, the county health officer. “Everyone should continue to have a plan to stay cool and help others do the same.”

Emergency room visits for heat-related illness rose sharply this week. Temperatures in Portland reached 103 F (39 C) on Thursday — 20 degrees above average.

Temperatures that were expected to soar to triple digits in Portland on Friday were somewhat suppressed by a thick veil of wildfire smoke.

Although the smoky haze may have brought some relief to sweltering temperatures in Oregon, it was also the cause of air quality alerts.

One such alert was issued through Saturday for much of northwestern Washington because of smoke drifting in from blazes in the eastern part of the state and British Columbia. Meanwhile, the sky over Portland had an eerie orange glow.

Forecasters said hot weather and smoke from wildfires in the Northwest would pose a problem through the weekend.

The West is experiencing a more than 20-year megadrought that studies link to human-caused climate change.