FORECAST SUMMARY: Thursday July 2nd, 2026, through Monday July 6th, 2026
Ozone:
Ozone concentrations are expected to be in the Moderate (Yellow AQI) range.
PM2.5:
PM2.5 concentrations are expected to be in the Moderate (Yellow AQI) range.
FORECAST DISCUSSION:
Ahead of the 4th of July holiday weekend, Michiganders wake up to yet another hot temperature and high humidity day with some relief on the horizon this weekend.
The heat dome that has been over us this past week will finally start to move off to the east, but hot temperatures and humidity will hang around for at least the first half of the weekend. With the changing of pressure systems, a frontal boundary that has been lingering near the Straits of Mackinac will make its way southward on Saturday. With it, scattered and pop-up rain showers are expected across the state. Especially with humidity hanging around, it will not take much to fire off some rain showers or even storms, but it will not be a complete washout of a weekend, however.
This past week was rather interesting for air quality in terms of forecasting, although, for the most part, the two pollutants we forecast behaved. The high humidity played a significant role in dampening Ozone production in southeast Michigan and west Michigan. A few monitors exceeded the Unhealthy for Sensitive Groups range, but 8-hour Ozone averages remained in the mid-to-high Moderate, at worst. An interesting phenomenon happened yesterday, Wednesday, which can emphasize the impact humidity and high moisture levels can have on Ozone. Throughout the afternoon dew points were well into the 70s across Michigan, which is known to hinder Ozone development. However, for a few hours yesterday afternoon in west Michigan, dew points dropped to the mid-to-upper 60s due to a very localized area of dry air that was brought down from upper levels in the atmosphere. This timeframe seemed to have coincided with a few hour increase of Ozone on the west side of the state, more so at our Holland and Muskegon monitors. When there was relatively drier air at those monitors, Ozone was above the Unhealthy for Sensitive Groups range, and when more moist air was present, those concentrations decreased. The Ozone increase was also at peak heating and solar energy after multiple days of the same airmass, so the lower dew points could be a coincidence, but this goes to show how multiple factors need to be considered when forecasting Ozone. For this weekend, Ozone looks to behave with the aforementioned rain and clouds moving in.
For PM2.5, as always with the 4th of July weekend, fireworks will locally increase PM2.5 concentrations due to the smoke associated with the colorful displays. For a few hours, especially in metro Detroit and Grand Rapids, Unhealthy for Sensitive Groups range PM2.5 concentrations should be expected in the evening time and into the overnight hours throughout the weekend. As of now, there appears to be enough of a breeze to help clear out and disperse the firework smoke so increases should only last a few hours.
Aside from firework smoke, wildfire smoke looks to be swirling around our neighbors to the north. Looking at the Canadian wildfire map, comparing now to a week or two ago, the number of fires has just about doubled. The current heat dome impacting us here has also been impacting Canada by providing dry conditions. Some of these fires that have just started are rather close to us in western Ontario and eastern Quebec. Smoke from these fires is visible on satellite imagery, but thanks to the southerly flow we have had for the past week, smoke has been remaining in Canada. However, we will have to wait and see what happens when we get a wind shift to a northwest-northeast direction which looks like might happen next week.
Both Ozone and PM2.5 will be monitored throughout this weekend, so if any conditions change and warrant an updated forecast, an update will be made.
EXTENDED FORECAST:
We get some relief from the heat, but not by much as the mid-80s look to remain into next week. With lowering humidity, Ozone will have to be watched along with wildfire smoke in Canada. Air quality will remain in the Moderate range.
Next Forecast update: Monday July 6th, 2026