Portland | An early heat wave took hold Saturday in parts of the Pacific Northwest, with temperatures at or near record levels in some areas and heat advisories in place through Monday.

The historically temperate region has grappled with scorching summer temperatures and unprecedented wildfires fuelled by climate change in recent years.

The National Weather Service issued a heat advisory extending from Saturday through Monday for much of the western parts of both Oregon and Washington state. It said the temperatures could raise the risk of heat-related illness, particularly for those who are dehydrated or don't have effective cooling.

Temperatures in Portland, Oregon, were expected to be in the low-90 degree F (32 C) range over the weekend, according to the National Weather Service. The temperature at Portland International Airport as of mid-afternoon Saturday reached 92 F (33.3 C), tying a 1973 record, said Gerald Macke, a meteorological technician with the weather service in Portland.

The temperature at the Seattle-Tacoma International Airport was 84 F (28.9 C) as of mid-afternoon Saturday, with warmer temps expected in the region Sunday, said Trent Davis, a meteorologist with the weather service in Seattle. The record temperature for the airport Saturday was 85 F (29.4 C), he said, a mark last hit in 2018. It could reach 90 F (32C) at that location Sunday, he said.

The unseasonal high temperatures could further flame the dozens of fires burning in Canada's western Alberta province, where officials have ordered evacuations and declared a state of emergency. Residents and officials in the Northwest have been trying to adjust to the likely reality of longer, hotter heat waves following the deadly “heat dome” weather phenomenon in 2021 that prompted record temperatures and deaths across the region.

Elizabeth Romero and her three children were among those cooling off at a fountain in downtown Portland on Friday afternoon.

"We decided to stop by ... until we all feel better," she said, adding that she plans to seek out shaded parks during the weekend.

King County, home to Seattle, directed transportation operators such as bus drivers to let people ride for free if they're seeking respite from the heat or heading to a cooling centre. The county's regional homeless authority said several cooling and day centres will be open across the county.

Authorities also urged people to be wary of cold water temperatures, should they be tempted to take a river or lake swim to cool off. River temperatures are probably in the low- to mid-40s (4.4 to 7.2 C), National Weather Service meteorologist Higa said.

Residents and officials in the Pacific Northwest have become more vigilant about heat wave preparations after some 800 people died in Oregon, Washington and British Columbia during the heat dome weather event in late June and early July 2021. The temperature at the time soared to an all-time high of 116 F (46.7 C) in Portland and smashed heat records in cities and towns across the region. Many of those who died were older people who lived alone.

In response, Oregon passed a law requiring all new housing built after April 2024 to have air conditioning installed in at least one room. The law already prohibits landlords in most cases from restricting tenants from installing cooling devices in their rental units.

Last summer, Portland launched a heat response programme with the goal of installing portable heat pump and cooling units in low-income households, prioritising residents who are older and live alone, as well as those with underlying health conditions. Local nonprofits participating in the programme installed more than 3,000 units last year, according to the city's Bureau of Planning and Sustainability.

Officials in Multnomah County, home to Portland, said they weren't planning on opening special cooling centres for now but are monitoring the forecast and can do so if needed.

“This is the first significant event … and it is early for us,” said Chris Voss, the county's director of emergency management. “We're not seeing a situation where we are hearing that this is extremely dangerous. That being said, we don't know if it's going to drift.”