The National Weather Service said temperatures were expected to be near 100 degrees Fahrenheit Thursday in Portland, Ore., with Seattle expected to see highs in the lower 90s, CNN reported.
The coastal region was under an excessive heat warning
At least 70 large fires were burning in 13 states west of the Mississippi River, the National Interagency Coordination Center said. California had the most with 13 blazes, followed by Nevada with 12 and Idaho with 10, the center said.
Marine helicopter units from California joined U.S. Air Force Reserve and Air National Guard units from Colorado, Wyoming, North Carolina and California Wednesday to fight the fires by air, officials said.
The NWS said a weather pattern developing in parts of Oregon could produce conditions that could yield "explosive fire growth," CNN said.