Heat islands that boost temps affect majority of Portlanders
Add Axios as your preferred source to
see more of our stories on Google.
More than 70% of Portland residents live on heat islands with temperatures that feel at least 8° higher than surrounding areas, a new analysis shows.
Why it matters: Urban heat islands (UHIs) are boosting temperatures within 65 major U.S. cities that are home to 50 million people, or 15% of the total U.S. population, according to Climate Central's analysis of 2024 temperatures.
- Nearly 34 million people nationally live in environments where UHIs could raise temperatures by at least 8°F.
Zoom in: Portland reached record highs each day from July 5-9 and saw a seven-day streak of highs over 90° from July 4-10.
- Over the past week, temps in Portland have been in the upper 80s to upper 90s each day, which is "warmer than normal," David Bishop, a meteorologist with the National Weather Service in Portland, told Axios.
How it works: Heat islands — urban hotspots with higher temperatures compared to surrounding areas — are created when roads, buildings, parking lots and the like "trap" heat.
- Often such neighborhoods, which tend to be poorer, lack trees and plants that would otherwise help cool the area.
Driving the news: Contributing factors driving the UHI index are built environments, such as roads, buildings and parking lots, a reduced percentage of green space with insufficient plants to help cool the air plus dense populations.
- "The entire planet is warming due to human-caused climate change, but the built environment further amplifies both average temperatures and extreme heat in cities," per a Climate Central statement announcing the new data.
What they're saying: "Urban heat islands already expose residents to disproportionate heat risks and cooling costs, which will only climb as long as carbon pollution drives up global temperatures," said Climate Central's Jennifer Brady in a statement.
Caveat: Scientists factor the heat island effect into their climate change monitoring and projections, and it does not explain the sharp uptick in global average temperatures, melting glaciers, record ocean warmth and more.
The bottom line: Cities are increasingly understanding the need to combat the heat island effect by adding more green space, using reflective paint on roads and buildings, opening cooling centers and more.
- Portland has an Equitable Tree Canopy program which includes planting at least 15,000 trees on public and private property and maintaining the trees already there to combat urban heat islands.
What's next: NWS Portland forecasts 10 days of cooler highs, in the 80s rather than 90s, starting this weekend.