What was the deal with all the haze in Evansville last week?

EVANSVILLE — The air quality in and around Evansville has fluctuated wildly over the past month as smoke from wildfires in Canada drifted in and out of the Tri-State area. But last week was different.

On Tuesday and Wednesday, the skies around Evansville and many other Midwestern cities noticeably darkened. Air quality figures plummeted. People with lung conditions were urged to stay inside, and the layers of thick haze were visible for everyone to see.

But why?

Dr. James M. Durbin, an associate professor of geology at the University of Southern Indiana, said large-scale weather conditions in the region have been "completely backward," and that laid the groundwork for smoke from Canadian wildfires and particulate matter to inundate Evansville.

"We're in a bit of a weird atmospheric circulation pattern," Durbin told the Courier & Press. "The wind patterns are a little bit odd right now, and it has been influencing our weather over the last three to four weeks."

Typically, summer storms and pressure systems hit the Tri-State area from the west. But recently, two major storm systems moved in from the opposite direction – the Northeast – and created the perfect conditions for smoke from the Canadian wildfires to funnel into the Midwest, Durbin explained.

"That pushes the weather patterns," he said. "If you look at the satellite photos, you can see the smoke streams coming in from the north, and it's just a direct corridor right to us."

Durbin also said human-caused climate change and warming temperatures expose huge swaths of forest, including in Canada, to prolonged droughts and dry conditions. That makes large-scale fires more likely.

"Human-caused global warming is certainly an issue," he said.

So far this year, Canada has experienced the worst wildfire season on record. By early June, the blazes had scorched more than 9 million acres of land in both eastern and western regions of the country. Many of the fires are still burning unchecked.

Forecasters noted that Thursday's severe weather helped to improve Evansville's air quality into the weekend as temperatures rose and smoke drifted back to the northeast.

As of Friday morning, fine particulate matter in the air around Evansville had decreased substantially, according to the Indiana Department of Environmental Management. However, the entire state remains under an "Air Quality Action Day" due to elevated ozone levels.

Tools to monitor air quality and forecasts

The Indiana Department of Environmental Management hosts an online tool it dubs SmogWatch that allows users to view real-time data from air quality monitoring sensors across the state.

IDEM also notifies the public when air quality devolves to the point that spending time outside could be unhealthy for Hoosiers with lung conditions.

More: Here's what to do - and not do - when the air quality is bad in Evansville

The U.S. Environmental Protection Agency hosts a free website called AirNow that provides air quality data and forecasts nationwide.

If you're looking for a quick check of the air quality in your area and you have an iOS device, Apple's updated Weather app features a detailed air-quality index map and will notify users when local air quality alerts are issued.

Evansville and cities across the country could face another hurdle this week, when millions of people unleash Fourth of July fireworks. Those explosions can also negatively affect air quality.

Houston can be contacted at houston.harwood@courierpress.com

This article originally appeared on Evansville Courier & Press: Why smoke and air quality impacted the Evansville area last week