Trent Cullinan of Sargent Corporation wipes sweat from his face while taking a break from construction work on Preble Street Extension on Tuesday. Derek Davis/Staff Photographer

A third straight day of oppressive heat and humidity is on tap for Maine on Wednesday, but relief from the scorching temperatures should arrive overnight, the National Weather Service said.

Portland on Tuesday tied its record high of 96 degrees, a mark set in 1944, at the Portland Jetport at 2:55 p.m., according to weather service meteorologist Chris Kimble.

With just one day left to sweat through, this is shaping up to be Maine’s hottest June on record, Kimble said. The June record was set in 2001 with an average temperature of 67.1. But this year, the average temperature stands at 67.8 and that is not likely to change by the end of the day Wednesday.

Kimble said the National Weather Service is forecasting a high of 94 Wednesday in Portland. If that happens, Portland and most of Maine will have experienced an official heat wave – defined as three consecutive days of highs of 90 or higher. Sunday’s high was 87, but highs of 97 and 96 were recorded Monday and Tuesday in Portland.

Things should start to cool down late Wednesday, accompanied by scattered, severe thunderstorms packing heavy rain and damaging winds starting in the afternoon. Forecasts call for a high of about 81 forecast for Thursday and 68 for Friday, Kimble said. In the meantime, the weather service is urging people to stay hydrated and seek shade or air conditioning whenever possible. A heat advisory will be in effect from 11 a.m. through 8 p.m. Wednesday.

Wednesday’s heat index will be dangerously high, the combination of heat and humidity making it feel like 100 degrees, Kimble said. That happened Tuesday around 4 p.m. in Portland with the temperature reaching 96 and the heat index making it feel like 101 degrees.

More records could be tied or broken Wednesday. Portland’s high of 96 degrees for June 30 was recorded in 1971.

“It’s not out of the question, we could tie or set a new record on Wednesday,” Kimble said, adding that it has not been this hot in Maine since 2016, when a high of 99 was recorded in Portland on Aug. 12.

The combination of extreme heat and lack of precipitation prompted the South Berwick Water District to issue a mandatory water conservation notice Tuesday. The outdoor water conservation measures will remain in place until further notice.

Water customers are being asked to refrain from all outdoor uses of water including the use of sprinklers and irrigation systems, washing vehicles and filling swimming pools.

Cities and towns across Maine opened cooling centers Tuesday and Wednesday, according to the Maine Emergency Management Center.

Among the cooling centers open Wednesday are the Augusta Civic Center 8 a.m. to 5 p.m.; Falmouth Ice Center on Hat Trick Drive from 4 a.m. to midnight; the South Portland Community Center from 6 a.m. to 9 p.m.; and the Troubh Ice Arena, 225 Park Ave. in Portland, from 9 a.m. through 4 p.m.

Beaches were a popular destination Tuesday. Popham Beach State in Phippsburg reached capacity at 11 a.m. and was forced to turn away visitors.

Power outages plagued some communities Tuesday, but Central Maine Power Company said it has been closely monitoring the power distribution system.

“Persistently hot days create a huge demand for energy,” CMP tweeted Tuesday night. “CMP is closely monitoring the system through the heat and proactively managing the demand to provide reliable power.”

Nearly 1,500 CMP customers in nine counties were without power as of 8 p.m. Tuesday. The number of outages dropped to 854 at 9 p.m. Only 329 Versant Power customers were without power Tuesday evening. Versant serves customers in northern and Down East Maine.

Maine is not alone in its suffering. A record breaking heat wave has been scorching the Pacific Northwest with temperatures regularly exceeding 100 degrees. Portland, Oregon, hit 108 Saturday, 112 Sunday and 116 on Monday.