SALEM — El Nino didn’t cause Washington’s record heat in May and probably will have a “modest at best” effect on the summer, but it may end a streak of large snowpacks, State Climatologist Nick Bond said Thursday, June 8.

The National Oceanic and Atmospheric Administration announced that an El Nino has formed, the first since 2019. El Nino tilts the odds in favor of a warm and dry winter in the Northwest.

It’s still a weak El Nino, but NOAA’s Climate Prediction Center estimated there’s a 56% chance that by late fall it will strengthen into the first strong El Nino since the winter of 2015-16.

For the past three winters, a La Nina, associated with cooler and wetter winters in the northern U.S., has prevailed. The La Nina finally faded in late winter.

“We’ve benefited from a disproportionate number of La Ninas,” Bond said. “The El Nino is a problem because of what it’s going to do to next year’s snowpack.”

As El Nino took shape, Washington’s average temperature in May was 6.4 degrees above normal, tying 1958 for the state’s hottest May, according to the National Centers for Environmental Information. Oregon and Idaho each had their fifth-warmest Mays on records. Records go back to 1895.

Bond attributed the record month to persistent weather patterns unrelated to the formation of the El Nino. “I don’t think we can really blame El Nino for what we’ve seen so far,” he said.

Bond said he expects the summer to be hot and dry based on global weather models and trends: “Recently our summers have been warm and dry, so there’s reason to think it will stay that way.”

As a rule of thumb, La Nina and El Nino have opposite effects. With an El Nino, California and the Southwest may get cooler weather and more rain in the winter.

Oregon is more likely to have a mild winter during an El Nino, but El Nino’s dividing line between warm and cold winters could fall somewhere in Oregon, State Climatologist Larry O’Neill said.

La Nina’s effects the past three winters have been unpredictable, and that will be the case with El Nino, he said. Ironically, “very strong” El Nino Oregon winters have been unusually wet, he said, adding that “every El Nino or La Nina is a little bit different.”

El Nino, which triggers changes in the atmosphere, will need time to influence the weather.

“In the short term for this summer, I’m not expecting any real impact we can trace back to El Nino,” O’Neill said.

Washington’s hot May changed the summer water outlook. Snow held 34.4 million acre-feet of water May 1. By May 18, the snowpack was down to 17.3 million acre-feet, according to the state Department of Ecology.

Much more water than usual ran down the Columbia River in May at The Dalles Dam. Less water than usual will run down in June, the Northwest River Forecast Council predicted.