Greater Puyallup area among the hottest places in Pierce County, new study says
Cities in the greater Puyallup area are among the hottest places in Pierce County.
A study from the Pierce County Office of Resilience and Climate Action, a division of Pierce County Planning and Public Works, says places like Puyallup, South Hill and Sumner are some of the most at-risk communities for extreme heat.
The study, which came out in July, highlights the ongoing challenge of extreme heat in East Pierce County. According to the National Weather Service, a heat advisory is in effect until 10 p.m. Tuesday night for Puyallup and elsewhere in the South Sound. A high near 95 degrees is expected on Tuesday, with temperatures in the 60s and 70s expected the rest of the week.
The report defines extreme heat as “a period of abnormally hot and dangerous temperatures … that can result in negative impacts to people, animals, and infrastructure.”
How did this study happen and what did it find?
According to the study’s website, volunteers used heat sensor equipment to collect air temperature across Pierce County on Aug. 4, 2024 – a “high heat day” with temperatures forecasted over 85 degrees across the area. Researchers prioritized areas with important “community hubs” such as schools, parks and community centers.
Between 6 a.m. and 7 a.m., temperatures were relatively low – but Fife and Sumner had the highest temperatures at 62 degrees, due to warehouses in those areas trapping heat overnight, according to the study.
In the afternoon, between 3 p.m. and 4 p.m., temperatures in inland areas reached up to 87 degrees – a 10-degree difference from areas near the Puget Sound, such as Gig Harbor and Lakewood. Puyallup, South Hill and Sumner are among the areas marked in red, which indicate the highest temperatures.
When researchers measured temperatures again between 7 p.m. and 8 p.m., they found that warehouses and industrial areas along state Route 167 – such as Puyallup, South Hill, Sumner and Fife – retained heat for longer. This contrasts with areas like Parkland, Spanaway and Frederickson, which got hot during the afternoon but cooled off at night.
Puyallup, South Hill, Sumner and Fife remained the hottest areas due to the warehouses and industrial areas retaining heat, according to the study. Gig Harbor and Lakewood were the coolest communities throughout the day.
What causes extreme heat in some areas?
The study says impervious surfaces, human activity, lack of tree cover and distance from shorelines can all increase the heat in certain areas.
Concrete, asphalt and buildings absorb heat, the study says, and retain it even at night.
“Some of the hottest areas in Pierce County have large paved areas, like the South Hill Mall parking lot,” the study says. “The dark color of the asphalt and the lack of shading concentrates heat, and the asphalt continues to radiate heat at [8 p.m.]”
Human activities can also radiate heat, the study says, by driving cars, manufacturing goods and using energy such as air conditioning. In areas with more people and buildings, these activities can increase temperatures.
“In cities, these human activities are concentrated in places with denser populations and more buildings, adding extra warmth to the air and making the area hotter,” the study says. “Buildings can trap this heat and stop cool air from flowing through the neighborhood.”
Trees and plants can lower temperatures by providing shade and releasing water vapor, the study says. Areas with fewer street trees can see hotter temperatures.
Finally, inland areas are likely to be hotter than areas by the water, since breezes from lakes or the Puget Sound can lower temperatures. The study says this could be the reason Gig Harbor and Lakewood were the coolest areas in the county throughout the day. Bonney Lake – which is by Lake Tapps – also remained relatively cool and stable as the day went on.
What can residents do to stay cool?
Officials say it is important to know the signs of heat exhaustion and heat stroke.
Heat exhaustion can include dizziness, excessive sweating and pale, clammy skin. It can usually be treated by moving to a cool space and drinking water. If left untreated, heat exhaustion can turn into heat stroke.
Heat stroke can result in confusion, unconsciousness, lack of sweat and red, dry skin. If you suspect you are suffering from heat stroke, call 911 immediately.
“During periods of extreme heat, it’s crucial to check on vulnerable neighbors like the elderly, young children, and those with chronic health conditions,” the study says. “Offer assistance like providing transportation to a cooling center or simply checking if they need water.”
Pierce County also provides cooling centers every summer, the study says. To see the hours and locations of each cooling center, visit PierceCountyWa.gov/Ready.
