As a withering heat wave scorched the Boston area for a fifth day, forecasters warned that dangerous levels of heat and humidity would peak Friday and persist through Saturday, a stifling summer blast that could make July the hottest on record.
The oppressive weather, which has enveloped the Northeast and Midwest throughout the week, prompted heat warnings, drew thousands of Boston residents to air-conditioned community centers, and caused electricity demand to surge to near-record levels.
“Typically in a heat wave, demand on the grid grows day by day,” said Ellen Foley, a spokeswoman for ISO New England, which operates the region’s electric power system. “The higher the dew point, demand grows that much more.”
On Wednesday, demand peaked at more than 26,000 megawatts, the 10th highest mark on record. With demand expected to remain high Friday and Saturday, ISO New England asked people to conserve electricity when possible, particularly between noon and 8 p.m.
Temperatures may climb into the upper 90s in Boston Friday and near 100 in some inland areas, topping 90 degrees for the 11th time this month. Health officials urged the public to stay out of the sun and keep hydrated.
With the muggy weather, environmental officials also issued an air quality advisory for southern coastal Massachusetts and sections of Connecticut and Rhode Island. Despite the dangerous conditions, few heat-related illnesses were reported.
“In general, things are going well,” said Nick Martin, spokesman for the Boston Public Health Commission. “It seems people are heeding the warnings and not staying out for long.”
Thousands of Boston residents sought relief at one of the city’s designated air-conditioned community centers, and employees at housing developments for elderly and disabled residents went door to door to make sure people were staying cool.
The prolonged heat wave also threatened to shut down the nuclear power plant in Plymouth, as water used to cool its system surpassed regulatory limits for the longest stretch on record.
The Nuclear Regulatory Commission requires that water drawn from Cape Cod Bay to cool the Pilgrim Nuclear Power Station not exceed 75 degrees. On Wednesday, water temperatures topped that level for more than five hours, requiring the plant to reduce power levels temporarily.
Water temperatures have not surpassed that mark since then, but could as the heat wave persists. Temperatures would need to exceed the limit for 12 hours for the plant to shut down.
“Obviously, they are going to have to keep an eye on it,” said Neil Sheehan, a spokesman for the Nuclear Regulatory Commission, which regulates the plant. “They need to have sufficient heat transfer.”
Last August, a reactor in Connecticut was shut down for two weeks because of high water temperatures, the commission said.
When the limits were put into place, regulators never thought they would be a concern, Sheehan said. But rising water temperatures have brought the limits within reach.
“No one could envision a scenario where water temperatures would exceed these limits,” Sheehan said.
While a sea breeze made things a bit more tolerable in Boston Thursday, temperatures reached the mid-90s inland. At 3 p.m., Fitchburg, Orange, and Springfield had recorded temperatures of 95 degrees, according to the National Weather Service. Friday was looking worse, with temperatures soaring to the mid- and upper- 90s, even on the coast.
“We don’t often issue excessive heat advisories,” said Kim Buttrick, a meteorologist with the National Weather Service. “We will likely issue another one tomorrow.”
The temperature is expected to top 90 again Saturday, extending the heat wave to seven days. The record is nine straight days, set in 1912.
In Boston, where highs this time of year are usually in the low 80s, the prolonged heat was taking a toll, even more so for some Jamaica Plain residents who lost power yesterday afternoon.
Nathan Schmidt, 32, who lives in Jamaica Plain, said he needed to pick up a prescription by early afternoon, but his regular pharmacy was closed, and no other branch would fill his prescription.
“I need this today,” he said. “I’ve lived here seven years, and this hasn’t happened before.”
Danielle Dearmon, 29, said she lost power a few times last week, once for about 12 hours. One time, she waited it out in her living room, the only room with air conditioning, enjoying the lingering cool air before the heat overwhelmed it. The other time, she escaped to Carson Beach.
At Q Salon & Spa on Centre Street, owner Jennifer Lydon sat with a few of her colleagues. The power went off about 12:30 p.m., just as stylists were in the middle of cuts and colors.
“It got hot in here very quickly,” she said. “We finished what we could, since we obviously couldn’t leave clients with half a haircut.”
As hot as it was, some were not complaining. Mind over matter, they said.
“Being in the AC all day isn’t healthy for you,” said Catherine Iannuzzo, 60, who said she believed in being outdoors as much as possible. “If you accept the weather, you adapt. And there’s even a breeze out today.”
That breeze might abandon us Friday, but relief was in sight. Forecasters saw a good chance of rain and thunderstorms Saturday evening, and Sunday was expected to bring seasonable temperatures in the low 80s, with lower humidity. That should hold for a few days at least, forecasters said.
“Right now, it looks like temperatures will remain seasonable throughout the week,” Buttrick said.