With the heat index on its way to 109 Tuesday, the hottest day so far this year, strangers at unshaded crosswalks exchanged anguished scowls. Commuters trudging from place to place seemed to move in sweaty slow motion.

"Intense," said a SEPTA worker, loading jugs of bleach and cleaning supplies onto his truck.

"Miserable," said the food cart owner, grilling hot dogs inside.

"Should be illegal," said a man dressed up as a Continental soldier in a toasty wool vest and long linen pants.

All of these patriots will be back at it Wednesday, when temperatures will cool only slightly to the low 90s. No air-conditioned indoor get-togethers or beachy breezes for them. Independence Day is a working day. And it's going to be a steamy 242nd.

July 4 at its hottest will feel like 98, with the heat index. After dark, it will be humid with a light wind. The record temperature for an Independence Day in Philadelphia was 103 in 1966.

Early Tuesday morning, Dominick Mireles helped direct the setup of six "mist stations" and three water-bottle fill stations along the Parkway. Thousands are expected to come out for the planned musical festival and fireworks show. Staff from the city's Office of Emergency Management pushed giant sprinklers and 8-foot-tall fans into position to prepare.

>>READ MORE: 6 cool ways to get out of the heat this summer in Philadelphia

"We're throwing all of our weight at it," Mireles said.

A lot of sweat goes into keeping people cool.

On the Fourth, the OEM staff will monitor the Parkway, along with hundreds of cops, firefighters, and paramedics working the celebration.

"I don't mind the heat," said John Buriak, a Center City District employee who will be directing hot visitors Wednesday.

The former bartender, who lives in Frankford, said he likes any job where he gets to talk to people. He doesn't find people to be ruder when temperatures rise, but they do seem to move more slowly.

A widower with a daughter and two grandkids living in New Mexico, Buriak hasn't had a Fourth of July off in about 20 years. But he celebrates on the job with the city, he said. "It's not so bad. You just have to find your little patch of shade."

Lifeguard Hosni Knox, 18, opens an umbrella at the Lee Cultural Center pool in West Philadelphia.
TIM TAI / Staff Photographer
Lifeguard Hosni Knox, 18, opens an umbrella at the Lee Cultural Center pool in West Philadelphia.

On Tuesday, his patch was under the awning of Lindsay Moffei's "Little Italy" food cart. Moffei, of Cherry Hill, serves up hot dogs, Italian food, and water ice every day on the corner across from the Liberty Bell.

She's stocking up for the crowds on Wednesday. "Extra water, extra sodas, extra, extra, extra ice," she said. The little metal trailer really heats up when someone orders a cheesesteak. "Sometimes I'll just pour cups of ice water down my back," she said. When she gets home she'll shower and celebrate a hard day's work with a drink.

"Red wine," she said. "With ice cubes."

Around noon Tuesday in the refreshing air-conditioning of the Kimmel Center, saxophonist and UArts professor Ron Kerber rehearsed with the Philly Pops. His concerts in front of Independence Hall and on the Parkway on Wednesday will be decidedly hotter.

"Temperature really affects the pitch of an instrument," Kerber said. "If it gets too hot. you can go sharp. I play a metal instrument. Hot metal to your face doesn't feel very good."

It's Kerber's 19th year with the Pops. "I know this is America's holiday, but it really is Philly's holiday," he said. "And to play in that space is so cool. We've got the statue of Washington right in the middle of us." (The General's likeness is between the brass and woodwinds sections.)

When 14-year-old Connor Cooke gets hot on Independence Mall, as one might when wearing a Continental soldier's uniform, he thinks about the Battle of Brandywine, where most deaths were heat-related. Cooke is one of about a dozen members of the West Jersey Artillery Company who dress up like the New Jersey soldiers who serviced the cannons under George Washington.

"You can read the books about what it was like to be a soldier, marching all day, fighting all day, but this way you get to experience it a little bit," said Cooke, a sophomore at Delsea High School in Franklinville.

Philadelphia pools are all open on July 4 (noon to 5 p.m.), so that means Kaia Taylor and Hosni Knox, both 18, will report for their lifeguard shifts in West Philadelphia.

Yes, it's sweltering sitting up there, baking, on days like these. And yes, there's something a little bit tortuous about watching people splash around in a pool you can't jump into on a whim.

But Lee Pool is where both of them learned to swim when they were little. A hot July day here is wrapped up in summer memories of swim camp and swim-team meets.

All of a sudden, they're nearly grown-ups, remembering their younger selves in the little kids splashing around below them. Taylor has a swim scholarship to Merrimack College in Massachusetts. Knox will start at the Coast Guard Academy next year. They both plan to return during their summers off to lifeguard.

"This is home," Knox said. "They're my family. So to be honest, being here on the Fourth is where I'd want to be."

Staff writer Anthony R. Wood contributed to this article.