Air quality in parts of western Montana deteriorated rapidly overnight.

NBC Montana reported as of 9:30 a.m. on Saturday morning, air quality in the Missoula Valley was listed at Unhealthy, and outside, the smell of smoke was noticeable, and visibility, limited.

Air quality in the Bitterroot Valley was even worse, listed at Very Unhealthy in some places, according to the Montana DEQ.

Missoula County Air Quality Specialist Ben Schmitt those with heart or lung disease, smokers, children, and the elderly should avoid heavy or prolonged exertion and stay indoors when possible. The general population should limit prolonged exertion and limit time spent outdoors.

Some of the smoke, according to Schmitt, is coming from the Wildhorse Point Fire, burning south of Huson.

Schmitt said irritants in the smoke could affect people more than smoke from a more distant fire and smoke conditions in this area could change rapidly.

Click here for more health related smoke information.