"We do know that this is particularly unhealthy for sensitive groups and those sensitive groups are people with lung disease, older adults as well as younger children," said Boise nurse Monica Cavazos.
When the air quality gets bad, many people have trouble breathing.
"My son had asthma for awhile and you can definitely see it, because he had a chronic cough and it definitely affects him," said Boise resident, Jim Essany.
The polluted air that's been trapped in the valley for weeks, isn't getting the attention it should, because people are more focused on the freezing temperatures.
"The cold takes priority in your brain, you don't know that the air is orange," said Boise resident David Rudeen.
But even with the cold temps: the poor air quality is hard to miss. "You can't see. I think the inversion with the way it is, it's so dry, it's blocked in everything so it's created what looks like a layer that's kind of sitting on Boise right now," said Boise resident Josh Wiechman.
Symptoms of the poor air quality include: eye irritation, sore throat and coughing.
KBOI meteorologist Vin Crosby said Monday there's a chance the inversion may be weakened by mid-week.