The heat wave is triggering some unhealthy environmental effects, making it tougher for some people to breathe, and forcing others to be careful where they take a swim.

Emissions of chemicals that lead to ground-level ozone pollution are generally going down. But UW-Madison environmental studies professor Tracey Holloway says long stretches of hot sunny days cook the emissions that do come from gas-powered vehicles and fossil-fueled power plants. And the heat also boosts emissions from natural sources like trees and plants. So Holloway says we still get jabbed, right in the lungs.

Holloway says sensitive populations — including children, the elderly and people with asthma — feel it the worst, but she says the ozone pollution can cause tightness in almost anyone's chest. If you're trying to beat the heat by jumping in a lake, the DNR warns that blue-green algae blooms are popping up in waters across the state.

The DNR's Susan Graham says hot weather interacts with nutrients in the water to trigger the blooms. She says many lakes do not have big algae problems. But if your favorite lake does, people and pets should be kept away, as some of the blooms create toxins. The DNR says a dog exposed to blue-green algae reportedly died this week in Oneida County.