Haze and smoke returns to Denver Air quality alert in effect for the Front Range Meteorologist Stacey Donaldson has your forecast for 7/25 - temperatures warming up and last updated 2021-07-25 19:32:30-04 DENVER- Afternoon highs were in the 90s for metro Denver this Sunday afternoon. We have thunderstorms in the mountains as well, however, most of the intense, heavy rainfall will be farther south- into Arizona and New Mexico. We have Flash Flood Watches in effect from Aspen to Vail for our central mountains until Sunday evening. An Ozone Action Day Alert is in effect for the Front Range through Monday afternoon. Ozone concentrations in the Unhealthy for Sensitive Groups category are possible Sunday afternoon and evening, particularly from the western suburbs of Denver, northward along the foothills through Boulder, to the Ft. Collins area, along with southern parts of Weld County. Smoke and haze is returning to the metro which contributes to the higher ozone levels.