Pollutant Overview
Ozone (O₃):
8-hour average ozone concentrations are expected to range from Good (Green AQI) to Moderate (Yellow AQI). A small chance for USG (Orange AQI) exists in southeastern and southwestern Michigan on Thursday.
Fine Particulates (PM-2.5):
PM2.5 concentrations will be Moderate across southern Michigan, with USG levels developing in the Upper Peninsula Thursday afternoon, expanding into the northern Lower Peninsula by early Friday morning. There is a possibility of short-term Unhealthy (Red AQI) spikes in localized areas.
Forecast Discussion
A frontal boundary advancing south through Michigan will be the focal point for storm development and air quality impacts over the next few days.
Thursday: Warm and humid conditions persist with sunshine and temperatures reaching 80s in the north and 90s in the south. Heat indices may approach 100°F in parts of southern Michigan.
Precipitation will move into northern areas late Thursday, spreading further south by early Friday as the front progresses.
As the front moves south, Canadian wildfire smoke will be pulled into Michigan. Forecast models indicate:
Smoke entering the Upper Peninsula Thursday afternoon
The smoke plume will drift into the northern Lower Peninsula early Friday morning, potentially reaching central areas by midday Friday.
PM2.5 levels are expected to rise into the USG (Orange AQI) range in the advisory areas. There is also a chance for hourly concentrations to briefly reach the Unhealthy (Red AQI) range. The advisory will be reevaluated Friday morning to determine if expansion further south or an extension into Saturday is necessary.
For ozone, some monitors reached low-end USG levels in southeastern Michigan on Wednesday. A similar risk exists for Thursday, particularly in southeastern and southwestern Michigan, though most areas are expected to remain in the Moderate range.
Extended Outlook
The extended forecast remains uncertain due to:
The path and intensity of additional smoke plumes
The timing of precipitation
The ongoing impact of heat and humidity on air quality levels
Further forecast updates will be issued as conditions develop.