Think Out Loud

Oregon meteorologist talks heat wave, causes and what’s next

By Alex Hasenstab (OPB)
July 9, 2021 1:25 p.m.

When the recent heat wave broiled the Northwest, some meteorologists started to question the validity of historical climate comparisons, as our past is increasingly disconnected from our present, let alone our future.

Meanwhile, a team of scientists has tied the heat wave to human-caused global warming, saying in a paper published Wednesday that it would have been “virtually impossible” without climate change.


Larry O’ Neill is Oregon’s state climatologist and an associate professor in Oregon State University’s College of Earth, Ocean and Atmospheric Sciences. In an appearance on OPB’s “Think Out Loud,” O’Neill reflected on the early forecast before the record-breaking heat wave arrived in the Pacific Northwest.

“About 10 days before the event, the forecast models that we usually rely on to give us guidance on weather forecasts began to show this very unusually strong weather pattern developing,” O’Neill said. “The temperature forecasts in Washington and Oregon and British Columbia were absolutely insane.”

The forecasted temperatures, ranging from 110 to 120 degrees Fahrenheit in the Pacific Northwest, extending into British Columbia, were unheard of in historical data. O’Neill said many meteorologists were in disbelief.

“The conversation quickly turned to what is wrong with these models,” O’Neill said, “and why are they doing something that’s obviously not going to happen?”

The expected temperatures were so far out of the realm of normal, that meteorologists assumed there was an error. But, as the days passed, it became clear that wasn’t the case.

“The models very consistently stuck to that story, and it became clear that we were seeing something that was in fact going to be a historic heat wave,” O’Neill said.

Why it happened

The heat wave resulted from a high-pressure system that developed off the coast of British Columbia. At first, O’Neill said, it looked like a lot of heat waves the Pacific Northwest has experienced in the past, but scientists quickly realized this one was different. First, the average temperature throughout the atmosphere was much warmer than normal.

“The second thing is that the heat wave was actually interacting with very severe to extreme drought conditions,” he said.

Some scientists hypothesize that the lack of moisture in the soil may have limited its normal role of cooling the air through evaporation.


“We’re still kind of working out exactly what the mechanism was for why this extreme event happened,” he said.

The heat wave was so extreme that new all-time high temperature records were set. Portland broke its historical record by 9 degrees Fahrenheit.

“It’s just the magnitude that it broke, it was really surprising and it wasn’t just one day,” O’Neill said. “It was it was three days of extremely warm weather.”

Scientists across the nation have concluded that the extreme heat wave would not have occurred without human-caused climate change, the result of burning fossil fuels like coal, gasoline and natural gas. O’Neill says that while the analysis was done quickly and without peer review, he believes it holds up, as it is consistent with decades of research.

“The conclusion that global warming, or climate change, had a significant impact on this heat wave, I think, is a fairly robust conclusion that agrees with other lines of evidence too,” O’Neill said.

O’Neill anticipates more extreme heat events in the future and says that areas not used to extreme heat must learn to adapt.

“It’s the first ones that we start experiencing that cause the most public health impacts, the most infrastructure impacts,” O’Neill said, “because it’s the ones we haven’t experienced, the ones we haven’t planned for.”

In the decade to come, he expects more difficulties for a region that is still built for a cooler climate.

“It’s going to be harder for us to deal with until we start to adapt to basically having a different climate,” O’Neill said.

On Tuesday, the state of Oregon announced that the number of deaths attributed to heat had risen to 116. And many experts have said that the death toll will continue to undercount the actual number of people who lost their lives because of the heat wave.

The impacts on people’s lives will also be felt in other ways, O’Neill said.

“This heat wave basically moved up fire season a little bit more by drying out fuels,” O’Neill said. “We can’t predict wildfire with any accuracy, but we can say that the risk of wildfire is very high from this point forward until we get those first wetting rains in the fall.”

The National Weather Service has forecast another heat wave, issuing an excessive heat warning for Friday across California. This one may not be historic, O’Neill said.

“Some of the forecasts are actually projecting it to be kind of prolonged,” he said. “And so, coming on the heels of the heat wave we just had, the impacts might be actually more severe, especially for public health and agriculture.”