Montclair has opened up township locations as cooling centers for those who need relief from the ongoing heatwave.

The measure comes after Monday night saw at least the third incidence of blackouts and brownouts in the township amid extreme heat in recent weeks.

Lauren Ugori, a spokesperson for the utility company, said there were two issues causing Monday night's outages — both equipment failures, and neither related to the heat.

One caused outages for about 1,200 customers out — some seeing service come on and off —  but all were restored by about 10 a.m. Tuesday, she said.

A second equipment issue, a transformer failure, affected 44 customers "and it’s going to take longer to restore," Ugori said Tuesday morning.

"We’re working on it as safely and quickly as possible, but that may run into the early evening, she said. We really appreciate our customers' patience."

Reports of power outages and traffic lights out had come in from the areas of Claremont Avenue and Valley Road, Harrison Avenue and Union Street, Grove Street and Glenridge Avenue, and Pine Street and Glenridge Avenue, Montclair Police Sgt. Terence Turner said.

The National Weather Service said Tuesday an excessive heat warning would remain in effect until 8 p.m. Wednesday, with heat index values of up to 104 degrees. It warned hot temperatures and high humidity could cause heat-related illnesses.

"Seniors and those with chronic health problems or mental health conditions are at an increased risk," the NWS said in its advisory. "Homes without air conditioning can be much hotter than outdoor temperatures."

It urged residents to use air conditioning to stay cool, and to go to a place with air conditioning if it's not available at home. It also suggested checking on vulnerable friends, family members and neighbors.

Montclair Animal Control Officer Michele Shiber advised pet owners to keep their pet indoors.

"We know that people love to spend time with their pets, including running errands with them, but when the heat is so high, keep your pets at home," she said. "It's better to leave your pet at home with the AC instead. Even running inside and leaving the car on for a couple of minutes, anything can still happen. It becomes a dangerous situation. The pet could go into heat stroke.”

She said pet walks should be kept short, and it's best to avoid hot pavement.

"It’s usually the hottest between 11 a.m. and 1 pm, so try to walk your dog before or after that," Shiber said. "Keep clean and fresh water accessible to them at all times and pay attention to signs of overheating. The No. 1 sign is excessive panting. Remember to supervise your pets around the pool. Not all of them are good swimmers.”

Montclair's cooling centers are as follows:

• Montclair Municipal Building Council Chamber, 205 Claremont Avenue. Cooling center hours: Tuesday, Wednesday and Thursday from 8:30 a.m. to 4:30 p.m.

• Montclair Public Library main branch, 50 South Fullerton Avenue: Tuesday from noon to 7 p.m. and Wednesday and Thursday from 10 a.m. to 5 p.m.

• Montclair Public Library Bellevue Avenue branch, 185 Bellevue Ave.: Tuesday and Thursday from 10 a.m. to 2 p.m.

As of Tuesday morning, Montclair Police hadn't issued any tickets or citations for heat-related offenses, like leaving children or hot pets in cars, Turner said.

— Lauren Peacock and Louis C. Hochman