Thousands of Massachusetts Eversource customers were left in the dark, and without air conditioning and lights, after a heat-related problem at an Acton substation on Wednesday, an Eversource spokesperson said.
National Grid also reported a "major power outage" in Medford amid Wednesday's 90-degree temperatures, police said.
Nearly 11,000 customers lost power around 4 p.m., but most customers had their power restored within an hour, according to Eversource spokesperson Chris McKinnon.
"When you're talking about a five-day stretch of 90-plus-degree weather, which is not what we typically experience here, there's always a chance for the added load onto the system," McKinnon said. "So what we're doing at Eversource is making sure that we're monitoring our system."
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As of around 11:45 p.m., customers in Medford had power back, and more than 1,400 remained in the dark in Acton. Outages in Falmouth were affecting more than 8,400 customers.
According to McKinnon, with the possibility of power outages during the heat wave, you should make sure your cellphone and other necessary electronics are charged ahead of time.
The estimated restoration time for the remaining Acton customers, as of Tuesday evening, was 4 a.m on Wednesday.