Many communities across the region issued this summer's first hot weather heat warnings Monday.

John Corcoran, deputy director of the Montgomery County Public Safety Department, says those with mental illness are particularly vulnerable during the heat wave expected to continue through Saturday.

"Going outside and dressing in layers, when they should be doing quite the opposite," Corcoran said "And the medicines they take. They can affect their blood pressure, they can make them more susceptible to dehydration."

County staffers are making calls and checking in with existing clients but Corcoran wants help identifying other vulnerable residents.

The cooling center locations in Montgomery County include the Coordinated Homeless Outreach Center on the grounds of Norristown State Hospital and the Pottstown office of the Salvation Army.

In Bucks County, senior centers are staying open later than usual this week to give people a place to cool off.

In Philadelphia, the Occupational Safety and Health Administration is fielding calls from construction workers.

"People should drink water even if they are not thirsty every 15 minutes. Rest in the shade. Wear hats and light-colored clothing," she Judy Posusney, assistant director of the Philadelphia OSHA office.

She also worries about people toiling away in humid industrial kitchens and laundries.

"Sometimes when you are working, you are not thinking about the last time you had a glass of water," Posusney said.

OSHA does not have specific rules on the number -- or length -- of breaks workers should get when temperatures rise, but it offers several tools, including a smartphone app, to help employers help their employees avoid heat illness.

Philadelphia's Heatline is 215-765-9040. It operates from 8:30 a.m. until 12 a.m. through Friday.

Tough to pay attention in school

Sweltering heat and the humidity also made it difficult for some West Philadelphia students to focus Monday.

"Lots of complaints," said Meg Ferrigno, director of the summer enrichment Freedom School program at Huey Elementary in the Cobbs Creek neighborhood.

"We have fans all around," Ferrigno said. "It's hard for the teachers to speak over the fans. So, the students would rather stay at home, some of them have (air conditioning) at home, but we don't have AC in our classrooms. So they are complaining that they want to go home, or they want to go swimming."

Ferrigno said her program budget doesn't allow her to buy window air-conditioning units, but she's hoping a generous donor will step up to help make her students more comfortable — and focused -- on their work.

The program at Huey is just six weeks long and was canceled four times last year because of excessive temperatures. In Philadelphia, the school superintendent makes the final decision on school closings after consulting with operations staff.

In Delaware, there's an excessive heat warning for New Castle County through Wednesday. Reminders from the state Division of Public Health include tips to make sure kids aren't left in overheated cars.

"Even with the windows cracked open, a car's interior temperatures can rise almost 20 degrees Fahrenheit within the first 10 minutes," according to the Centers for Disease Control and Prevention.

Some of the steps to protect children include:

• Never leave children alone in a car -- even for one minute.

• Place a necessity -- a cell phone, PDA, purse, briefcase -- on the floor in front of your child in the back seat. This will force you to open the back door.

• Have a plan with your child-care provider to call if your child does not arrive when expected.

• Check cars and trunks first if a child goes missing.