A 600-acre wildfire in north-central Washington's Union Valley has prompted the evacuation of about 20 homes.

Lt. Maria Agnew of the Chelan County sheriff's department and emergency management office says the fire was sparked by lightning shortly before 9 p.m. Tuesday and was fanned by erratic weather.

She says residents of another 75 to 100 homes have been advised to be prepared to evacuate if necessary.

Union Valley is east of Chelan, a small resort community on the shore of Lake Chelan. The Red Cross has set up a shelter at the Chelan high school.

Agnew says the fire has burned some public utility lines, but so far no structures have been damaged.

KOZI-AM reports that the state is sending firefighting resources in the form of a Type 3 team that is expected to arrive Wednesday morning. A more specialized fire management team is to arrive for a briefing at 2 p.m.

"Brutal" temperatures are predicted for the Seattle area on Wednesday as a record heat wave afflicting the Pacific Northwest continues to bake everything west of the Cascades, a National Weather Service meteorologist said.

The high temperature could easily tie or break the all-time record temperature of 100 degrees set July 20, 1994, at Sea-Tac, the weather service's Jay Albrecht said.

"There's not going to be a whole lot of places to get away from the heat tomorrow," he said Tuesday.

Another day of high heat for the normally temperate region follows a Tuesday that saw the thermometer hit 106 at Portland International Airport, just short of the 107 all-time mark for the area set in 1981.