As we enter the heart of the summer, we're also entering the peak time for ozone smog pollution. So far, it's been a pretty average ozone season, with only a couple Ozone Action! Days.

Weather plays the key role in creating unhealthy levels of ozone smog. Here's what to look out for: first, it needs to be hot. The chemical reactions that make ground-level ozone don't really get cranking until temperatures reach 90 degrees or so. String a couple days like that together and there's the potential for ozone problems.

Second, the weather needs to be stagnant, with not much wind. If winds are light, any ozone that forms will hang around and build up, rather than get dispersed. But even if there's some wind, there can still be ozone problems. That's because many states to our west and southwest have a lot of industrial and power plants, so winds coming from those directions can actually turn their pollution problems into ours.