Air pollution around much of the state will be at unhealthy levels for some people between midnight Wednesday and Thursday afternoon, according to the Minnesota Pollution Control Agency (MPCA).

It issued a yellow air alert for fine-particle pollution, which increases the risk for heart attacks, strokes and lung-related diseases for the elderly, children and others with health issues. It could be more severe in some parts of the state.

The problem is the result of a combination of low clouds, fog and light southeasterly to easterly winds, said Frank Kolasch, the MPCA’s air quality expert.

The peak will be during the morning rush hour, and much of central and southern Minnesota will be affected.

The alert will continue into the late afternoon hours on Thursday, when conditions are expected to improve as increased northwesterly winds begin to disperse pollutants.

Kolasch said that such winter air alerts for fine particles also occurred during the last El Niño, the weather phenomenon tied to this year’s drier, warmer winter in the Upper Midwest.

“The last time we had a strong El Niño, we had a number of days where the weather systems set up like this,” he said.

The southeasterly winds are bringing in air pollution from other cities, which is combining with the pollution produced in the Twin Cities and driving it to unusually high levels, he said.

Populations sensitive to fine particles include those with preexisting cardiovascular or respiratory diseases, the elderly, children, and those who participate in activities requiring extended or heavy exertion, both indoors and outdoors.

Kolasch said people in those groups should postpone or reduce vigorous activity and minimize exposure to local sources of air pollution — heavy-duty vehicle traffic, wood fires and candles.

Even individuals who are otherwise healthy may experience health effects when pollution levels increase.