The Colorado Department of Public Health and Environment has issued the following. WHAT. Ozone Action Day Alert. WHERE. Douglas, Jefferson, Denver, western Arapahoe, western Adams, Broomfield, Boulder, Larimer, and Weld Counties WHEN. 400 PM Wednesday July 16 to 400 PM Thursday July 17 IMPACTS. Ozone Action Day Alert is now in effect for the Front Range Urban Corridor. Ozone will remain in the Good to Moderate range on Wednesday. Warming temperatures and light winds may allow ozone to reach levels that are Unhealthy for Sensitive Groups on Thursday. The highest concentrations are expected along the western portions of the northern Front Range, from western Denver northward to Fort Collins. For Colorado air quality conditions, forecasts, and advisories, visit: https://www.colorado.gov/airquality/colorado_summary.aspx If possible, please help us reduce ozone pollution by limiting driving gas and diesel-powered vehicles until at least 4 p.m. Thursday, July 17, 2025. Colorado is also addressing ozone pollution through state policies. For more information about health impacts and how ozone pollution forms in Colorado, visit: https://cdphe.colorado.gov/ozone- pollution-and-your-health HEALTH INFORMATION. Increasing likelihood of respiratory symptoms and breathing discomfort in active children and adults and people with lung disease, such as asthma. Active children and adults, and people with lung disease, such as asthma, should reduce prolonged or heavy outdoor exertion.
