FORECAST SUMMARY: Friday September 11th, 2026, through Monday September 14th, 2026
Ozone:
Ozone concentrations are expected to be in the Good (Green AQI) to Moderate (Yellow AQI) range, with the potential of hourly Unhealthy for Sensitive Groups (Orange AQI) concentrations.
PM-2.5:
PM-2.5 concentrations are expected to be in the Good (Green AQI) to Moderate (Yellow AQI) range.
FORECAST DISCUSSION:
High pressure is currently sitting over southeast Michigan providing lights winds and ample sunlight this Friday morning. This system will slowly move to the east as today carries on but clear skies and temperatures in the 70s should be expected throughout the day. Saturday looks to provide a slight warm up into the low-80s as a warm front just clips the southern portions of Michigan and turns the winds to a more southwesterly direction. This frontal boundary may pop-up scattered rain showers in the morning hours, but nothing to cancel plans over as they are expected to be light, if any produce. Later on, Saturday evening, the next frontal boundary, a cold front, will move across the state from the west, which will bring our temperatures back down to where they were on Friday with the exception of the upper peninsula which will see temperatures hanging around the 60s. With the cold front passing through, winds will shift to a north-northwesterly direction which will carry into Monday before shifting more to the east.
For air quality, southerly flow tomorrow will allow for PM2.5 concentrations to increase into the low-Moderate range. With the shifting winds on Sunday, especially from the north, cleaner air will be present allowing for PM2.5 concentrations to decrease into the Good range. Ozone, on the other hand, looks like it wants to increase tomorrow, Saturday, for portions of southwest Michigan. Today, Friday, looks like it may be what we call a “ramp-up day” where precursors of Ozone gather and weather conditions that are conducive to Ozone development start to come into place. On Saturday, with the shifting winds to the southwest, these ingredients in place may allow for Unhealthy for Sensitive Groups (USG) concentrations of Ozone to develop in the southwest corner of Michigan along the Lake Michigan shoreline. The only kicker to this set up is the amount of clouds that produce in that corner of the state. Michigan will be between two systems tomorrow, one with the aforementioned warm front, the other with the cold front coming on Sunday. So, the potential of clouds will increase throughout the day on Saturday as both systems and fronts make their way east. As of now, it looks like southwest Michigan will see scattered to overcast skies for much of the morning, before clearing in the mid-to-late afternoon. It will be interesting to see how long the clouds last, if they produce, and how the duration of the clouds inhibits the development of Ozone. If the clouds last longer, the atmospheric reaction that produces Ozone will be delayed until more sunlight makes it to the surface. If there is a lack of clouds, then Ozone may produce quicker and sooner than expected. With these uncertainties in place, along with it being September and the sun angle along with sun intensity being lower, I am expecting the Ozone 8-hour average to be in the mid-high Moderate range on Saturday. As mentioned above though, USG concentrations for a few hours cannot be ruled out.
EXTENDED FORECAST:
A slight cool down is on the docket for next week with air quality in the Good range.
Next Forecast update: Monday September 14th, 2026