Bay Jimmy, La. ? In the oil-fouled marshes of the Mississippi River delta, the sizzling high-noon heat beats down like a fist.

There’s hardly a breeze to stir the reeds dotted across the tea colored water, but Allen Sreiy is covered from the chin down by a white plastic suit, his feet in bright yellow boots, hands in thick blue plastic gloves.

Sreiy’s Tyvek suit, worn by hundreds of workers cleaning up oil along the Gulf Coast, protects crews from the crude but it also makes for a sweaty — and potentially dangerous — mess as a sweltering heat wave sweeps across the region.

“Whatever the temperature is, you put on this suit and you add 30 degrees just like that,” Sreiy said.

Sreiy, 24, and his father, Siphan Sreiy, would normally be shrimping this time of year, going out in the cool of the evening and working all night. But with fishing grounds closed by the oil, they signed up for a cleanup program called “vessels of opportunity.”

They are putting their boats to work pulling up oil-soaked boom instead of catching the seafood that New Orleans chefs turn into culinary works of art.

“It doesn’t pay as well as shrimping,” said Sreiy, who is from Buras, La. “But at least it pays.”

If you can take the heat.

Forecasters issued an excessive heat advisory Monday for unrelenting high temperatures across the Gulf Coast states with heat indexes approaching 110 degrees. A heat index of more than 105 creates prime conditions for heat illnesses, according to the National Weather Service, which says heat kills about 175 Americans annually.

“It is a very dangerous situation,” said Dr. James Diaz, head of environmental and occupational health sciences at the LSU Health Science Center in New Orleans.

Heat issues are reviewed every morning, said BP spokeswoman Stephanie Shanks. On-site supervisors, she said, are responsible for the effect of the heat.

BP says more than 24,000 workers are assigned to the oil spill, but it’s unclear how many of them are dealing directly with heat problems. Many are deployed on boats; others march the shoreline cleaning up oil blobs that make it to beaches.

“People from this area would have an advantage,” Diaz said. “They would be acclimated to the heat and that really helps. People coming from areas that don’t have this heat and humidity are going to have an even worse time with it.”

Taslin Alfonzo, spokeswoman for West Jefferson Medical Center in Louisiana, said 70 workers had been treated for heat-related illness at a tent in Grand Isle. None was serious enough to require hospitalization.

In Orange Beach, Ala., cleanup crews were dressed in the Occupational Safety and Health Administration-required protective coveralls and drenched in sweat as they used shovels to remove the top few inches of oil-stained sand. With the temperature already at 96 degrees by early afternoon on Monday, forecasters said it felt like 112 degrees on the hot, white sand.

Generators powered big fans that were pointed under tent-like canopies where workers took breaks, and safety bosses reminded them to drink plenty of water.