Salow, who works for the city's Parks and Recreation Department, said, "I'm ultra-worried about Thursday and Friday," when the temperature is forecast to reach or surpass 100. The pool can let only 240 people swim at a time - 30 swimmers for each of eight lifeguards.
"The problem is what happens when we have 200 people waiting outside," said Salow.
This year, he has more help with crowd control. Philadelphia police are detailed to 48 pools to help staffers deal with uncooperative teenagers and other challenges.
"The police have been a big help," Salow said. Last year, people repeatedly cut down the fence surrounding the pool at night. That hasn't happened this year, and Salow thinks it's because the police have stepped up their patrols.
By Wednesday afternoon, so many people had wanted to jump in the water at Hunting Park that Salow and his staff had them swimming in shifts. They let people swim for 30 minutes, blew a whistle, told them to get out of the pool, and let the next group in.
"We let the people with the dry suits in and get the wet suits out of the way," Salow explained.
Elizabeth Haynesworth, who visits the pool daily with her two children, said she thinks the police are necessary.
"They have to have them because a lot of people don't listen to the lifeguards," she said.
Leo Dignam, deputy commissioner of the Parks and Recreation Department, said the city has stationed police at pools since 2009.
"Sometimes people aren't too happy about getting out of the pool, especially teenagers," Dignam said. "They'd start diving in. We'd have to start calling 911. A lot of times just the sight of the police creates a little bit more cooperative atmosphere."
On the hottest days, as many as 1,000 people come to some city pools, with the Kelly Pool in West Philadelphia among the most popular.
That makes for long and stressful days for the staff.
John Brady, who runs the Vogt Recreation Center in Mayfair, said he doesn't stop worrying until the pool closes at 7 p.m.
Are the adults watching the children closely enough? Is it smart for seniors who have had heart surgery to be at the pool? Is the heat too much for his lifeguards?
"I don't relax until I go home," Brady said.
A few feet away, a police officer stood on the pool deck.
Brady thinks the police presence encourages people to behave but said he needs them to intervene only "once in a blue moon."
Although one teenager leaving the Vogt parking lot muttered that the staff was too uptight, most swimmers said they thought the rules - no flotation devices allowed; swimmers must wear bathing suits, not street clothes - helped keep everyone safe.
"It's the best pool in town. It's pretty well-mixed [racially]. Everybody gets along here," said Kenny Olberholtzer, 45, a Tacony plumber who was splashing in the Vogt pool with daughters Megan, 11, and Allison, 5.
With water dripping from her hair and swimsuit, 10-year-old Cathy Julia volunteered that her favorite part of the pool was not the cool water.
"What I like about this pool is that it's safe here," she said. "The cops come here and they take care of us."
Contact staff writer Miriam Hill at 215-854-5520, firstname.lastname@example.org or @miriamhill on Twitter.