Finally, it's warm enough for the kids to play outside. Just tell them not to breathe, okay?

From Clean Wisconsin, an environmental advocacy organization in Madison: 

It's not something to be proud of: Wisconsin has the most unsafe air in the country today. For the fourth day in a row, the Department of Natural Resources issued an air advisory for Wisconsin. The EPA''s Air Quality Index (AQI) forecast shows about one-third of the state covered in orange, the highest level of concern in today's forecast for the entire nation.

"It is alarming that the frequency of these alerts is on the rise in Wisconsin," says Katie Nekola, energy program director for Clean Wisconsin. "Health officials are encouraging children, the elderly and those with lung disease and asthma to stay inside. Instead of restricting Wisconsin's most vulnerable citizens, we should be cleaning up our air by taking the biggest polluters - old, dirty coal plants - offline."

The advisory was issued because of persistent and elevated levels of fine particles in the air. These fine particles come primarily from combustion sources, including coal-fired power plants. These particles can get deep into lung tissue, making them difficult to exhale, especially for health-sensitive individuals. In Wisconsin, 41 coal units emit thousands of tons os soot, or fine particles, in to the air every day.

To view the nationwide AQI forecast, click here.