Visibility in Boise dropped to 7 miles Sunday afternoon, largely due to wildfire smoke coming from the southwest, according to the National Weather Service. Winds from the southwest are gusting up to 25 mph.
California's Rim Fire has burned about 134,000 acres since Aug. 17. Gov. Jerry Brown has extended a state of emergency to include the city and county of San Francisco because of the threat to utilities, The Los Angeles Times reports.
The U.S. Forest Service says 4,500 structures are threatened by the fire. About 2,850 firefighters are battling the blaze.
"Wind direction and placement of that fire couldn't be any better for putting smoke in here," said Boise-based meteorologist Dave Groenert. "Other fires around contributing, but that's been the main source over the last few days."
Storms to the west and east of the Treasure Valley could spark new fires Sunday and Monday, but they're not expected to bring winds or rain to scrub the smoke out of the Valley.
High temperatures in Boise on Sunday were in the low 90s, and that's what is in the forecast for the coming week though Monday should be slightly cooler, with a forecast high of about 88. Mid- to upper 80s is normal for late August in Boise.
August has been warmer than normal. The average temperature for the first 24 days of the month was 78 degrees 2.5 degrees higher than normal.