BOISE, Idaho (AP) — A wildfire burning in Oregon that’s kicking smoke into neighboring states is now the largest active blaze in the U.S., authorities said, and fire crews are bracing for a storm late Wednesday that’s expected to bring lightning, strong winds and the risk of flash floods.

The Durkee Fire, burning near the Oregon-Idaho border about 130 miles (209 kilometers) west of Boise, Idaho, shut down Interstate 84 for hours on Tuesday as the flames approached the vital link between the states. The freeway briefly reopened Wednesday, but then closed again as officials warned of frequent disruptions because of the nearly 400-square-mile (1036-square-kilometer) blaze.

The town of Huntington, Oregon, home to about 500 people, remained evacuated for a third full day, and authorities issued warnings about the coming storm to those who have remained behind. The storm could bring wind gusts of up to 75 mph (121 kph), lightning and heavy rain that could cause flash flooding and debris flows in recently burned areas, the Baker County Sheriff’s Office said in a Facebook post.

The Oregon State Fire Marshal’s office also cautioned residents about the risk posed by the storm and the expected “abundant” lightning. The agency has mobilized nearly 500 firefighters to help protect communities that could be threatened by wildfires nearby.

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The major electricity utility in the region, Idaho Power, warned customers to prepare for possible outages.

“Power outages and freeway closures are expected. In the event that the fire reaches the City of Huntington, there may be delays in assisting residents that have not previously evacuated,” the sheriff’s office said.

More than 60 significant fires are burning in Oregon and Washington alone, and Oregon has been plagued with hundreds of lightning strikes from thunderstorms that have started new blazes in bone-dry vegetation.

Already, the smoke from the Durkee Fire in Oregon was choking the air in Boise and beyond. An air quality warning was in effect for the entire region on Wednesday.

Patrick Nauman, the owner of Weiser Classic Candy in the small town of Weiser, Idaho, near the Oregon border, said driving into town Wednesday morning was “like driving into a fog bank, because it’s so thick and low to the road.”

Nauman’s shop is on the main intersection in town and is typically a popular spot to stop for lunch or a sugar fix, but customer traffic has dropped by half in the past few days as thick smoke and triple-digit temperatures dogged the region.

“Yesterday you could smell it, taste it, it just kind of hung in the back of your throat,” Nauman said of the smoke.

Mike Cantin, a meteorologist with the National Weather Service in Boise, said cooler air moving into the region Wednesday evening could stoke the Oregon fire. A red flag warning was in effect and the area has been suffering through a heat wave, including many days over 100 degrees Fahrenheit (38 degrees Celsius).

“With these winds showing up today, every little spark could get out of hand very easily. It could be a really hazardous situation very fast,” Cantin said. “Don’t light anything on fire and be very careful around grass.”