A southerly wind flow that began late Thursday improved air quality conditions in the Treasure Valley over the weekend — and that’s continuing Monday, according to the National Weather Service.
The Idaho Department of Environmental Quality upgraded Monday’s air quality forecast from orange to yellow, or moderate levels.
The preliminary data on actual air quality shows conditions have improved significantly. Here are the air quality index numbers: Friday, red (152); Saturday, orange (121) and Sunday, yellow (78). Monday we’re forecast to be in the yellow range (85).
Forecasters had expected wind patterns to shift from the south to the west/northwest by Sunday night but that’s going to happen Monday afternoon or evening, said Joel Tannenholz, a meteorologist at the Weather Service.
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It’s unclear if the shift will bring in smoky air from western fires.
“It’s not going to be 100 percent smoke-free,” Tanneholz said of Tuesday’s forecast. “I don’t think it’s going to be any worse than (Monday). Most of the smoke is from the central Idaho mountains.”
Fall weather is arriving this week. There’s a slight chance of thunderstorms on Tuesday, with the greatest chance of rain Tuesday night.
A cold front that’s coming Wednesday night and into Thursday morning will knock temperatures down. There’s a 40 percent chance of rain in the Treasure Valley Wednesday — but don’t expect a deluge.
Widespread showers and thunderstorms are in the forecast for Thursday but things will dry out for the weekend.
Friday morning will be chilly, with temperatures dipping down to the high 40s. The high Friday will be in the low 60s.
Saturday will also be cool, with a morning low of 42 at the Boise Airport and high of 68. The forecast high is 11 degrees below normal, and the low is five degrees below normal.