FRESNO, Calif. (KFSN) --The air quality in some parts of the Central Valley is at an unhealthy level even for those with no known breathing problems.
"Air quality is going to be at its worst during the afternoon when the temperatures are the hottest and the sun in the brightest," Jaime Holt with the Valley Air District said.
The sunny cities of Fresno, Visalia and Bakersfield are the most polluted in the country according to the American Lung Association.
But a heat wave is only making matters worse.
"We don't create more pollution in the valley than in other parts of the nation we actually create a lot less," Hold explained. But because we live in this bowl and have this weather patterns that trap pollution it just builds up day after day."
It's around this time of year you'd expect allergist Dr. William Ebbeling to be swamped, but that's not the case at least with current and former patients.
"The training of the patient to recognize these things prevents the problems," he said. "Patients who are taken care of for their asthma, they know what's good. It's when they don't follow the instructions that they start having problems."
Ebbeling also says one-third of yearly deaths related to asthma come from patients who weren't even aware they had a problem.
Mild persistent asthma shows no signs or symptoms in most patients and people only seek help when it's aggravated by issues like poor air quality.
"The important thing is, when it's red, nobody should be out there," Ebbeling said. "You should limit the amount of exposure you have outside. Period."