FORECAST SUMMARY: Monday, May 18, 2026 - Friday, May 22, 2026
Ozone: 8-hour average Ozone Particulate concentrations are expected to range between Good (AQI Green) and Moderate (AQI Yellow) through the forecast period.
PM-2.5: 24-hour daily average Fine Particulate concentrations will start the period mostly Moderate, with levels improving towards Good around mid-week.
FORECAST DISCUSSION:
A warm front will lift into the Upper Peninsula today, Monday, bringing summer‑like conditions to much of Michigan. South of the front, warm southerly winds will help drive temperatures into the mid to upper 80s. On Tuesday, a cold front sliding in from the northwest will bring a gradual cooldown from northwest to southeast. Even so, parts of southern Michigan may still reach the mid‑80s before the cooler air arrives. With the warm, humid, and unstable airmass in place, showers and thunderstorms are likely both Monday and Tuesday. A few storms could become severe, so be sure you have reliable ways to receive weather alerts. Quieter weather returns by midweek as high pressure settles in from the west. Sunshine dominates Wednesday through Friday, with temperatures on a slow warming trend.
Air quality will begin the period with mostly Moderate fine particulate levels across the state. As cooler northwest winds develop behind Tuesday’s cold front, particulate concentrations are expected to improve. Good concentrations are expected on Wednesday and Thursday before increases toward the low Moderate range return to southern Michigan on Friday.
Over the weekend, four monitors in west Michigan reached the lower end of the Unhealthy for Sensitive Groups (USG) ozone category on Saturday. Since then, ozone levels have ranged from Good to Moderate statewide. While warm temperatures and southerly winds can promote ozone formation, increased cloud cover and periods of thunderstorms will help limit more significant development. A mix of Good and Moderate concentrations continue on Monday and Tuesday. Statewide Good levels are forecast for Wednesday and Thursday, with a return to low‑Moderate readings possible by Friday.
EXTENDED FORECAST:
A frontal boundary positioned south of Michigan this weekend may trigger showers and thunderstorms, mainly across the southern part of the state. During the extended period, air quality is expected to remain at or below the Moderate range.
Next Forecast update: Friday, May 22, 2026