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File photo: Baton Rouge's India Banks chills out atop a picnic table, shaded by trees on the bank of University Lake as she relaxes on a day off at BREC's Milford Wampold Memorial Park, Thursday, Aug. 17, 2017. 

ADVOCATE STAFF PHOTO BY TRAVIS SPRADLING

Baton Rouge is on pace Thursday to set its second heat record this week.

The mercury climbed to 96 degrees on Tuesday, a new record. Thursday's forecast calls for a high of 93, the same as the high recorded on May 17, 1988, the current record-holder.

Lafayette, meanwhile, tied the record high on Sunday and crushed its record high on Wednesday by 5 degrees, clocking in at 95 degrees. The National Weather Service predicts the city will set a new record high temperature three out of the next four days.

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Around Baton Rouge, temperatures have risen into the 90s for days, and meteorologists expect them to stay there for several more.

While the weather may be unpleasant, it isn't quite as bad as 1922, when the heat rose into triple digits on four consecutive days back when the readings were taken near the confluence of the Port Allen Lock and the Mississippi River. They're measured at the Baton Rouge Metro Airport now.

Only one day this month — the fifth — has been cooler than the historical average in Baton Rouge, said NWS meteorologist Robert Ricks.

Besides the heat, officials worry about ozone buildup, which occurs when nitrogen oxides and volatile organic chemicals interact with the abundant sunlight.

Parishes around New Orleans have been put on alert throughout the month. So far only a small portion of the River Parishes have officially been measured as unhealthy for sensitive groups by the U.S. Environmental Protection Agency. Even then, it was only on one day — May 8 — though portions of southwest Louisiana have fared worse.

The stable, high-pressure system that has been hanging over the region prevents convection, which allows moisture and chemicals to rise into the atmosphere, diluting their concentrations, said state climatologist Barry Keim.

"The pollutants are just building up," he said.

There's some good news and bad news on the horizon. Temperatures are expected to drop in the coming days, and the Weather Service even predicts a 30 percent chance of storms Thursday.

As more humidity comes in from the Gulf of Mexico, it will help bring temperatures down, but it will also make the air muggier, Ricks said. So it may actually feel hotter than it has in the past week.

A tropical low disturbance pushing in from the Florida Panhandle should also help destabilize the high-pressure system that's been hanging over the region, Keim said.

The climate further west is even more stable than it is around Baton Rouge right now, he said. The Dallas and Houston areas have had much higher ozone rates. Generally, Texas and Louisiana's air pollution may make it hard for children, the elderly and people with lung issues to breathe, but on at least one occasion this month a region around Houston had air that could have been harmful even to healthy adults.

Follow Steve Hardy on Twitter, @SteveRHardy.