By Howard Monroe

PHILADELPHIA (CBS) – It’s going to be another hot day, and health officials in Philadelphia are taking it seriously. The city has declared a heat health emergency.

A heat emergency went into effect in the city at 8 a.m. Tuesday. That means the city will open cooling sites and also increase its homeless outreach. They’re even deploying SEPTA buses for people to cool off in.

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What makes the heat so dangerous is doctors say you can become dehydrated without even realizing it.

“Heat is a stress on the body, it’s a stress on the mind. It is uncomfortable to be hot for long periods of time,” Dr. Jennifer Vines, County Health Officer, said.

Figuring out ways to beat the heat. Kids and families packed into the city’s spray parks Monday afternoon. That may be a good bet for families because many of the city’s pools won’t be opening this summer. Only 47 pools will on Wednesday — that’s just 70% of pools in the city.

Philip Murray, of Philadelphia, said, “Kids here need recreations especially in the sweltering heat they have little relief but to go to the pool.”

Mayor Jim Kenney says they are having difficulty hiring lifeguards. The city’s parks and rec department says it’s been working around the clock to hire pool staff. Starting pay for lifeguards is now at $15 an hour with paid training. Mayor Kenney is blaming their struggles on the $200 of extra weekly federal unemployment benefits.

“Every industry in the country is having trouble getting people to go back to work,” Kenney said.

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“If you could sit at home and make more money people do that and I don’t know what each person’s circumstance is but its been shown in just about every place where they’re short workers that’s the problem they’re making more money staying in the air conditioning then standing by a pool,’ Kenney said.

The heat is especially troublesome in Philadelphia because of the heat island effect that’s caused by concrete radiating more heat. For people like construction workers and those who have to be outside, doctors say high heat can cause a wide arrange of problems from dehydration and heatstroke to an increased risk of heart disease and even death. Children and the elderly are the most susceptible but doctors say the heat can be harmful to everyone.

“So you might get nausea, headaches, light-headedness, muscle cramp,” health science expert Dr. June Spector said.

Doctors say even mild dehydration can impact your cognitive ability and mood. It’s best to stay inside as much as possible and drink plenty of water.

You can find a Philadelphia cooling center near you, here.

If you’re looking to cool off before the city’s pools open, sprinklers and spraygrounds are already open. Click here to see the locations.

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Click here for the full list of city pools opening this summer.