It’s been hot in Maine this summer, but not quite record-breaking hot.

At least not yet.

Temperatures in southern Maine topped 90 degrees Tuesday and are expected to do the same Wednesday, prompting school officials to dismiss students early and cancel sports practices, and sending people flocking to beaches.

And, by the end of this week, the burst of late-summer heat could push the summer of 2018 into record territory in Portland.

The warmest summer on record in Portland was 2016, when the average temperature during June, July and August was 68.9. Chris Kimble, a meteorologist with the National Weather Service in Gray, said the average temperature so far this summer was 68.8 degrees heading into Tuesday, with a few hot days in the forecast. The average summer temperature in Maine is 67.2, according to the weather service.

The balmy weather pattern this summer has also brought a noticeable measure of humidity, which made it feel even warmer.

“The air flow this summer has been pulling in warm, moist air from the Gulf of Mexico into New England. We’ve seen humid days more often,” Kimble said. “We’ve had less days with cooler, drier air moving in from Canada.”

Kimble said Portland typically sees five days a year that reach 90 degrees, but the city recorded its seventh 90-degree day Tuesday and will likely get one more Wednesday. The most 90-degree days ever recorded in a summer in Maine came in 1955, when there were 16 days that exceeded that number. There were 10 90-degree days in 2002, 2010 and 2013.

This summer has been more unusual because of its warm nights.

Maine has set a record for the number of days the temperature at night does not fall below 70 degrees, another indication of the how humid it has been, Kimble said. Before Tuesday, there were six days this summer — one in July and six in August — when the nighttime temperature stayed above 70, breaking the previous record of five days set in 2001 and 1988.

Because of the latest dose of hot air, the National Weather Service issued a heat advisory for Maine that will be in effect from noon Tuesday until 8 p.m. Wednesday, and the Maine Department of Environmental Protection issued a warning that ground-level ozone concentrations will reach unhealthy levels.

Heat advisories are issued when the heat index is expected to reach at least 105 degrees. The weather service predicted the heat index — combining temperature and humidity — would reach the upper 90s to low 100s on Tuesday and Wednesday.

The combination of hot temperatures and high humidity creates conditions in which heat illnesses are possible and people should take precautions, according to the weather service. It advises people to drink plenty of fluids, stay in an air-conditioned room and out of the sun, and check on older adults, especially those who live alone. The weather service also advises people to avoid strenuous activity or working outside, or to take frequent rest breaks in air-conditioned environments.

And, with the latest hot spell coming as the school year is just beginning in some districts, officials were already adjusting academic and athletic schedules Tuesday because of the weather forecast and the lack of air conditioning in Maine school buildings.

Students in Biddeford, Windham, Raymond, Gorham and Westbrook will all be dismissed early Wednesday — the first day of class in each district — because of the excessive heat. Students at Scarborough High School also will be dismissed early Wednesday. School officials in SAD 6 canceled open houses scheduled for Tuesday night and announced an early dismissal Wednesday.

The stretch of hot weather is welcome in coastal towns making a final push for a busy end to the peak summer tourist season. In Wells, traffic has been heavier than usual this year as people head for the beach, said Town Manager Jonathan Carter.

“It replicates 2016,” Carter said. “It’s been a great summer weather-wise.”

Old Orchard Beach is also wrapping up the beach season with a strong showing of people looking for relief from the heat.

“People are flocking to the beach,” said Capt. David Hemingway of the Old Orchard Beach Police Department. “The heat and humidity has certainly brought a steady flow of people into town.”

Despite the heat and humidity, Hemingway said there has not been a higher than usual call volume for heat-related illnesses.

“It seems like people have been pretty cautious in the sun down here,” he said.

For those looking for a little relief from the heat, there’s good news on the horizon. A cold front is expected to move through Maine on Thursday morning, bringing with it drier air and cooler temperatures.

“This air is coming straight out of the Arctic,” Kimble said. “Temperatures this weekend should top out in the 70s.”