A risk index for the heat enveloping a big swath of the U.S. grows progressively more severe for the Portland area through the July Fourth holiday weekend – peaking on Sunday when forecasters expect the hottest day of the wave here.
The predictions – generated for an experimental HeatRisk system created by the National Weather Service and U.S. Centers for Disease Control and Prevention – can help people understand how dangerous the weather is on any given day. Risk levels are updated daily.
The national map is color-coded to demonstrate heat risk from “none” to “extreme.” The weather service calculates how unusual the weather is for a given time of year, how long the heat wave will stretch, whether an area will cool down overnight and what health impacts the heat could have on sensitive populations.
You can find the index for your city in Oregon or across the country by zooming in and out on the map.
The national picture shows high heat risks across the South will ease over the next week while heat risks intensify on the West Coast.
“Moderate” heat risks on Thursday in western Oregon are expected to spread across the state on Friday, when areas west of the Cascades will start to see “major” heat risks.
Pockets of southwest Oregon, including Medford, are expected to see “extreme” heat risks as early as Friday.
The pattern escalates statewide on Saturday as heat intensifies east of the Cascades.
By Sunday, the heat risks are expected to ease in much of southwest Oregon, but remain escalated in Portland. The weather service now predicts a high of 103 degrees on Sunday.
The weather service map suggests that as heat risks fall west of the Cascades into early next week, the danger heats up in eastern Oregon.
By Wednesday, several parts of Oregon’s border with Idaho will hit “extreme” heat risk.
Here’s what the colors mean:
Green means the public doesn’t need to worry about any heat risks.
Yellow, or “minor” risk, suggests temperatures could have an impact on people who are extremely sensitive to heat, particularly if they’re outside or don’t have good access to a cool space or enough water.
Orange, for “moderate” risk, means most heat-sensitive individuals could see health impacts because of the heat. It also signifies that hospitals and heat-sensitive industries could start to see weather-driven ramifications.
Red means there’s a “major” heat risk. The heat at this level is expected to affect anyone without effective cooling or water, the National Weather Service says. Heat at this level is also likely to create a surge in emergency room visits and impact heat-sensitive industries and infrastructure.
The most severe risk level is purple for “extreme.” This signifies a rare or extended heat wave with little or no relief from temperatures overnight. At this heat risk, anyone without access to effective cooling or water is expected to experience health impacts. Impacts are “likely” in hospitals, heat-sensitive industries and infrastructure as well.
Sami Edge covers higher education and politics for The Oregonian. You can reach her at sedge@oregonian.com or (503) 260-3430.
Stories about the July Fourth heat wave
- Oregon heat wave topped out Tuesday at record-breaking 110 degrees in Hermiston
- 9 deaths now tied to excessive heat in Oregon
- Oregon coast businesses, hotels feel ‘bump’ from tourists escaping the heat
- West Linn drowning victim left life jacket on dock, first responders say
- Some school summer programming paused in Portland area due to lack of air conditioning