FORECAST SUMMARY: Friday, June 20, 2025 - Saturday, June 21, 2025
Ozone: 8-hour ozone concentrations are expected to range between Good (Green AQI) and Moderate (Yellow AQI), with USG (Orange, AQI) possible along the west Michigan lakeshore.
PM-2.5: 24-hour daily average Fine Particulate concentrations will range between Good and Moderate.
The Michigan Department of Environment, Great Lakes, and Energy (EGLE) has declared an Air Quality Advisory for June 21, 2025, for elevated levels of ozone in southwestern counties of Michigan. Pollutants within those areas are expected to be in the Unhealthy for Sensitive Groups (USG, Orange AQI) range.
The Air Quality Advisory is in effect for the following Michigan counties:
Allegan, Berrien, Kent, Muskegon, Ottawa, and Van Buren
FORECAST DISCUSSION:
Hot temperatures and humidity are the main forecast points for this weekend. Temperatures in the 90s, along with increased humidity, will make it “feel” like 100+ degrees in parts of the state. Those with outside plans should exercise caution. Forecast maps show a storm complex moving through the central and eastern areas early Saturday. There is a lot of uncertainty with the placement and timing of this complex, but any associated precipitation looks to end as Saturday progresses. This system looks to miss the west/southwest portion of the state. With ample sunshine expected in that portion of the state, along with a warm surface and upper-level flow, the environment will be favorable for ozone development. Because of this threat, we have issued an Air Quality Advisory for Saturday, which includes Muskegon and areas south to the state line.
The heat and humidity continue to build Sunday, and more in the way of sunshine is expected across the state. With there being a threat for ozone development to continue or expand, this forecast will be updated tomorrow.
Ozone will be the dominant pollutant through early next week. During this period, PM2.5 concentrations are expected to range from upper Good to middle Moderate.
EXTENDED FORECAST:
Extended models show the heat and humidity lingering into next week. We will be updating the forecast throughout the weekend do determine if air quality advisories are needed later in the forecast period.
Next Forecast update: Saturday, June 21, 2025