A car passes Serenity Worthley, 11, as she holds a lemonade Wednesday while tending her stand at her family’s house on Halifax Street in Winslow. Serenity is trying to stay cool as temperatures in the area hover around 90 degrees. Serenity, who cares for three cats, says she is donating half of the earnings from her stand to the Humane Society Waterville Area. Serenity, who opened her stand midway through the summer, says she has about $400 to donate. Rich Abrahamson/Morning Sentinel

AUGUSTA — In a hot twist to a cool, wet summer, record heat arrived Tuesday in central Maine and is expected to remain through Friday.

The National Weather Service posted a heat advisory from noon to 6 p.m. Thursday in Kennebec, Androscoggin and inland Cumberland and York counties, advising that weather conditions could cause heat illnesses.

Augusta’s high Thursday reached 90 degrees, tying the record set in 2007, according to Stephen Baron, a National Weather Service meteorologist at the Gray office. It was the second record-high temperature recorded this week in Maine’s capital city.

Several central Maine schools closed early or canceled after-school activities Thursday because of the heat.

The high temperature was forecast to be 88 degrees, but meteorologist Michael Clair said the humidity would make it feel hotter than that.

“We have seen (hot weather) before in September, but we are near the upper end of what we have seen before, like (Tuesday), with the record high,” said Clair, who also works out of the National Weather Service office in Gray. “It’s not every year, but it’s not unusual to see the 90s in September.”

Gardiner Area High School and Gardiner Regional Middle School were dismissed at 11 a.m., with the district’s elementary schools closing at noon.

Andrea Jones of Waterville holds an umbrella to create shade Thursday as she walks along Cool Street amid temperatures hovering around 90 degrees. Rich Abrahamson/Morning Sentinel

“While a few of our buildings have pockets of air conditioning, the majority of our classrooms do not, and three days into this weather pattern, we have classrooms in the 90s and buses that are even hotter,” said Patricia Hopkins, superintendent of Maine School Administrative District 11, in an alert posted on the district’s website.

In Winthrop, all public schools closed early for similar reasons.

Hallowell-based Regional School Unit 2 dismissed students early from all schools and canceled middle school athletics.

The Richmond school district canceled all after-school activities.

Peter Hallen, superintendent of Waterville Public Schools, said he toured many of the district’s buildings Wednesday, most of which are not fully air-conditioned. To beat the heat, teachers moved their classes into basements or into air-conditioned areas.

In the Skowhegan-area school district, Superintendent Jon Moody said windows in district buildings were being left open at night and some classes were moved into air-conditioned spaces. Recess was not canceled, and classes were taking breaks as needed due to the heat.

The temperature Tuesday also reached 90 degrees in Augusta, breaking the record of 88 degrees for Sept. 5, set in 1971. Clair said Augusta is the only site in central Maine for which the weather service has meaningful data, but conditions in Waterville and Skowhegan have been and are expected to be equally hot and uncomfortable.

By midafternoon Wednesday, the temperature in Augusta was 86 degrees, falling short of the record of 88 degrees.

But, at 69 degrees, the low temperature Wednesday did break the record of 68 degrees, set in 1983, according to Baron.

For most of the summer, Maine has been in a trough of low pressure, with cooler, wetter weather. Now as that has moved out of the region, it’s been followed by a high pressure ridge of hot weather. But, Clair said, since it comes later in the summer season, it is not going be like the heat the rest of the United States experienced earlier this summer.

A hazy sunset is reflected Wednesday on Maranacook Lake in Readfield. Such conditions in the region are the result of smoke from Canadian wildfires flowing across Maine, according to meteorologists. Joe Phelan/Kennebec Journal

Along with the daytime highs, the overnight lows will also be elevated, bringing little relief.

Clair said hot conditions will stick around Thursday and Friday, and begin to moderate Saturday. Next week, temperatures should drop back into the 70s.

In addition to the hot weather, hazy conditions over the region are the result of smoke from Canadian wildfires flowing across Maine.

The Maine Department of Environmental Protection issued an advisory Wednesday that the impact of the smoke is expected to affect the state Thursday and likely Friday. As of Wednesday, northern Maine was feeling the worst impact, but across central Maine, people who are sensitive to particle pollution are advised to consider reducing prolonged or heavy exertion. Coughing or shortness of breath are signs to slow down, and the advisory continues through Friday for much of the state, including central Maine.

Because so many variables affect air quality forecasts. the DEP does not typically issue forecasts beyond the next day.

Staff writer Dylan Tusinski of the Morning Sentinel contributed to this report.