Portland sees more extreme heat streaks as climate warms
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Periods of prolonged extreme heat are getting more common in Portland as climate change continues to warm the planet, according to a new analysis.
Why it matters: Streaks of hot days — as much of the U.S. has experienced this summer — are particularly hazardous to human health.
- Extreme heat's effects on the body tend to be cumulative, and warm nights offer little reprieve for those without air conditioning.
- Multi-day heat streaks are also challenging for power grid operators, given all the energy-intensive AC use.
Driving the news: The average number of annual extreme heat streaks rose between 1970-2024 in 80% of the 247 U.S. cities analyzed in a new report from Climate Central, a climate research group.
How it works: Climate Central defines an "extreme heat streak" as three or more days in a row with maximum temperatures over the 90th percentile of a given location's daily max temperatures during the 1991-2020 period.
- "Across the 247 cities analyzed, this temperature threshold ranged from 66°F in Juneau and Anchorage, Alaska, to 100°F in Yuma, Arizona," per the report, which is based on publicly available NOAA data.
Zoom in: Portland sees two more extreme heat streaks per year, compared to 1970, according to the report, in line with the national average.
- Eugene and Bend each saw two more as well, while Medford's total increased by one.
- That pales in comparison to some areas, like Nashville and Raleigh, that now have a whopping five more heat streaks on average each year.
Between the lines: Climate change is making extreme heat more intense and more frequent, studies have shown.
- Many urban neighborhoods — especially in East and North Portland — suffer from the "urban heat island" phenomenon, where buildings, roads and other structures trap heat, making it even hotter.
- Portland's most memorable heat streak was the 2021 heat dome, when temps spiked to 116°F and dozens were killed.
- Climate scientists found the record-breaking heat was "virtually impossible without human-caused climate change."