As temperatures continue to rise, ozone pollution is increasing.
Officials with the San Joaquin Valley Air Pollution Control District say as the heat reaches record levels, air pollution will also increase.
Residents are urged to stay inside not just to escape the heat but to avoid the small particles that can travel into their lungs.
The district also advised residents to look after each other, stay hydrated, and check their air filters.
Officials say high ozone pollution can cause asthma attacks, aggravate bronchitis, and increase the risk of heart attack and stroke.
Those with respiratory issues, the elderly, and those who are very young are the most at-risk.