Northwest Oregon had never seen anything like it. Over the course of three days in June 2021, Multnomah County—the state’s most populous county, which rests in the swayback along Oregon’s northern border—recorded highs of 108°, 112°, and 116° Fahrenheit.

Temperatures were so hot that the metal on cable cars melted and the asphalt on roadways buckled. Nearly half the homes in the county lacked cooling systems because of Oregon’s typically gentle summers, where average highs top out at 81°. Sixty-nine people perished from heat stroke, most of them in their homes.

When scientific studies showed that the extreme temperatures were caused by heat domes, which experts say are influenced by climate change, county officials didn’t just chalk it up to a random weather occurrence. They started researching the large fossil fuel companies whose emissions are driving the climate crisis—including ExxonMobil, Shell, and Chevron—and sued them.

“This catastrophe was not caused by an act of God,” said Jeffrey B. Simon, a lawyer for the county, “but rather by several of the world’s largest energy companies playing God with the lives of innocent and vulnerable people by selling as much oil and gas as they could.”

Now, 11 months after the suit was filed, Multnomah County is preparing to move forward with the case in Oregon state court after a federal judge in June settled a monthslong debate over where the suit should be heard.

About three dozen lawsuits have been filed by states, counties, and cities seeking damages from oil and gas companies for harms caused by climate change. Legal experts said the Oregon case is one of the first focused on public health costs related to high temperatures during a specific occurrence of the “heat dome effect.” Most of the other lawsuits seek damages more generally from such ongoing climate-related impacts as sea level rise, increased precipitation, intensifying extreme weather events, and flooding.

Pat Parenteau, professor of law emeritus at Vermont Law and Graduate School, said that zeroing in on the heat and the heat dome effect are elements that might make the Multnomah case easier to prove.

“When it comes to the extreme heat events that affected Portland, the scientists concluded, in looking at that event and then looking at historical records of heat waves in the Pacific Northwest, it would not have happened, but for human-caused climate change,” Parenteau said.

“That’s actually the first time I’ve ever seen climate scientists state a conclusion like that in such absolute terms,” he added.

Korey Silverman-Roati, a fellow at Columbia University’s Sabin Center for Climate Change, also said the case was distinctive because it focused on a specific event. “A lot of these other suits are alleging more long-term impact harm from climate change, like sea level rise is something that happens over the course of decades,” Silverman-Roati said. “Whereas the Multnomah suit is this 2021 heat dome disaster that they had to deal with.”

The Multnomah County lawsuit says that Exxon, Shell, Chevron, and others engaged in a range of improper practices, including negligence, creating a public nuisance, fraud, and deceit.

The suit alleges that the companies were aware of the harms of fossil fuels and engaged in a “scheme to rapaciously sell fossil fuel products and deceptively promote them as harmless to the environment, while they knew that carbon pollution emitted by their products into the atmosphere would likely cause deadly extreme heat events like that which devastated Multnomah County.”

“We know that climate-induced weather events like the 2021 Heat Dome harm the residents of Multnomah County and cause real financial costs to our local government,” Multnomah County Chair Jessica Vega Pederson said in a statement. “The Court’s decision to hear this lawsuit in State Court validates our assertion that the case should be resolved here—it’s an important win for this community.”

A spokesperson for Exxon declined to comment on the case; representatives for Shell and Chevron did not respond to requests for comment.

A common defense for fossil fuel companies is arguing that existing environmental laws, such as the Clean Air Act, are already responsible for regulating air quality so legal actions should not be allowed under state law, Silverman-Roati noted.