Con Ed crews were all hands on deck Wednesday night, trying to restore power as quickly as possible to thousands of customers.
About 1,700 customers were without power in Greenpoint on Wednesday afternoon.
Longtime Greenpoint resident Diane Sullivan sat on her front stoop, trying to find some relief from inside her stifling home.
"It's about 125," she said.
"Degrees?" CBS2's Andrea Grymes asked.
"Yeah, that's what it feels like," Sullivan said.
She's just one of more than 1,500 Con Edison customers who lost power in the neighborhood around 2:30 a.m.
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"It woke me up because I was really hot ... I went to the window and all the street lights were out," resident Lydia Richardson said.
Neighbor Angel Davila heard the power lines go up in flames, igniting a mattress at the curb.
"It just blew. You heard like a, pshooo! And then there was, like, fire in that bed. You could hear it, like, cooking it and the fire department showed up," he said.
One resident was so desperate, she bought a generator. Others picked up free dry ice from Con Edison on scene.
In Brownsville, the lights were off and elevators out of service at a six-story apartment building.
"There's no air conditioning. We are burning up. I mean, it's ridiculous," resident Trina Lugo told CBS2's Ali Bauman.
"This is really bad 'cause it's already hot, and then the apartments in there are really hot," resident Deandre Felix said.
Some of the buildings' hundreds of residents tried to stay cool outside. Con Edison estimated their power would be back Thursday afternoon.
"Whatever food we do have, we did try to bring it out, put it on the grill so it won't spoil," resident Tiara Carroll said.
"I'm very angry, yes. We're upset. We're hot, and we're upset," resident Latesha Mormon said.
Con Edison is dealing with day four of this oppressive heat wave.
"There are gonna be sporadic outages when you have this amount of heat and humidity and this amount of demand on the system," Con Edison spokesperson Jamie McShane said.
Crews have been working around the clock to make sure the grid stays operational and working to restore any outages as quickly as possible.
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They expect customers to far exceed last year's peak power usage.
"It's a strain. The demand, the demand for more power creates stress on the system. It's something that minutes matter," McShane said.
That's why late Wednesday afternoon, the mayor issued an urgent plea.
"We have a real challenge on our hands so here's the message to all New Yorkers -- immediately, immediately reduce the use of electricity in your home or in your business. This is very serious stuff. We need to ensure that our electric supply is protected," de Blasio said.
The city even sent out an emergency alert, telling New Yorkers to avoid using energy-intensive appliances, such as washing machines, dryers and microwaves.
Con Edison also reduced voltage in parts of Brooklyn and Queens to protect equipment.
In the meantime, Carroll has a message for Con Ed: "Please, please fix the issue!"
Many New Yorkers posted on social media Wednesday, asking why the city and Con Ed were urging residents to conserve power when Times Square was seemingly as brightly lit as ever.
Con Ed said it reduces voltage in areas where the grid is under stress and equipment is failing, and their request to conserve energy Wednesday was for all customers, including in Times Square.
A spokesperson for the mayor's office said City Hall spoke with the Times Square Alliance and asked all sign companies to conserve energy. The spokesperson said some were even turned off for a time.
CBS2's Andrea Grymes contributed to this report.
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