Tens of thousands of people across New York were left without power amid a heatwave that has put “severe strain” on the city’s electrical system.

More than 50,000 people suffered power outages, primarily in Brooklyn and Queens, with about 40,000 still without electricity on Monday morning.

Some 20,000 of those were residents of Brooklyn who were taken off power on Sunday so energy company Con Edison could make repairs to prevent a more widespread outage.

The power cuts occurred just over a week after a widespread blackout in midtown Manhattan and part of the Upper West Side that left approximately 72,000 people without electricity and disrupted subway services.

"We have been through this situation with Con Ed time and again, and they should have been better prepared – period," Governor Andrew Cuomo said in a statement.

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He added: "This was not a natural disaster; there is no excuse for what has happened in Brooklyn."

Mr Cuomo said he deployed 200 state troopers, 100 generators and 50 light towers to Brooklyn to help with the outages and urged New Yorkers to check on their neighbours, especially the elderly.

The governor has also directed the Department of Public Service to investigate Con Edison and the cause of the outages.

A press release by Con Edison said the outages were caused by “continued heat and high usage”.

New York's mayor, Bill de Blasio, said he was told by the company’s president that parts of the system in Brooklyn had come “under severe strain and some equipment [had] failed”.

Temperatures in New York reached highs of 35C on Saturday and Sunday following weeks of hot weather, with temperatures peaking in the low 30s.

The blackout earlier in the month was caused by equipment failure, not heat, affecting a 40-block stretch of Manhattan, including Times Square and the Rockefeller Centre.

“It's still hot and people have a right to be frustrated,” Mr de Blasio tweeted late on Sunday. “We're pushing Con Ed to get power back as fast as possible.”

New York's heatwave is expected to cool slightly over the coming days, reducing the strain on the power grid.