Louisville is under an air quality alert for soot this weekend—something that’s unusual for this time of year.

Most of the city’s air quality alerts are during the summertime, and for high levels of ozone. Air quality alerts for particulate matter are rare, but Air Pollution Control District spokesman Tom Nord said weird weather patterns forecast for this weekend are to blame.

“It’s not that we see any unusual amount of PM in the air, it’s more of an interesting weather pattern we’re seeing,” he said.

Louisville will have big storms to both the east and west this weekend, which will cause local air to be trapped in the Ohio River Valley and become stagnant.

The Air Quality Index (AQI) is predicted to be 101—just barely in the “orange” spectrum. When the AQI is between 101 and 150, it’s unhealthy for sensitive groups like children, the elderly and people suffering from respiratory conditions.

To check the air quality in real-time, visit AirNow.gov.