Jospeh Grimaldi, 5, left, and Leland Houdlette, 6, both of Portland, play in a wading pool at Deering Oaks on Tuesday. The two children, who did not know each other before Tuesday, recognized that they had the same sun hats and formed a friendship while playing at the splash pad to escape the heat. Derek Davis/Staff Photographer

Wednesday’s weekly outdoor yoga class at Payson Park is going to feel a lot more like hot yoga this week, with 90-degree temperatures and high humidity close to what studios cultivate for the exercise trend.

Portland could see some record-breaking high temperatures through Thursday as a heat wave moves into Maine for the first time in two years.

Temperatures are expected to reach the mid-90s in Portland on Wednesday and Thursday after hitting the mid 80s on Tuesday, and humidity could make it feel up to 96 degrees in the city, according to the National Weather Service in Gray. The agency has issued a heat advisory for southern Maine from noon to 8 p.m. – when temperatures are expected to peak – urging people to stay out of the sun, drink fluids and check on relatives and neighbors.

Other parts of the state, including Lewiston, Augusta and Bangor, are under an excessive heat warning, one of the most severe heat-related warnings the weather service issues. Heat and humidity could combine to make it feel as hot as 105 degrees in some of those areas.

Temperatures across the state are expected to remain high in the evenings – in the upper 60s and low 70s – which the weather service warned “will result in greater cumulative heat stress.”

While the mid-90-degree temperatures predicted for Wednesday and Thursday could break single-day records, they are unlikely to surpass the highest temperature on record in Portland in June, which was 98 degrees on June 28, 1991.

The highest recorded temperatures in Portland for June 19 and 20 were 94 degrees in 1995 and 93 degrees in 2020, respectively.

Higher temperatures are often accompanied by poorer air quality and increased ozone levels, prompting health concerns for at-risk populations such as children, older adults and people with respiratory or heart diseases.

Lamont Coggins and his daughter Amria Lockett, of Portland, sit near East End Beach on Tuesday after cooling off in the water. Ben McCanna/Staff Photographer

The Maine Department of Environmental Protection warned Tuesday afternoon that ground-level ozone levels are expected to reach unhealthy levels for sensitive groups on Wednesday from Kittery through Acadia National Park. The interior parts of the state are expected to reach moderate levels.

While ozone levels are difficult to predict several days in advance, people should still be wary of overexerting themselves in the outdoor heat, according to the agency.

“Even if ozone only reaches moderate [levels], you have that on top of the heat and humidity, and then you throw in moderate [particle pollution], and it isn’t just additive, it’s multiplicative,” said Martha Webster, an air quality meteorologist for the Maine DEP. “Even if ozone does not reach unhealthy for sensitive groups … there’s enough stress on people’s bodies that they should definitely be taking it easy and staying hydrated and staying as cool as they can.”

Webster noted that, regardless of their health risk, people should reduce their level of exertion and avoid exercising near busy roads where exposure to pollution could be increased.

Portland’s Kiwanis Community Pool and four playground splash pads will be open Wednesday, despite some services and City Hall shutting down for the federal Juneteenth holiday. Dozens of cooling centers will be open in York and Cumberland counties as well.

In Portland, The Troubh Ice Arena will open as a cooling center Wednesday from 9 a.m. to 4:30 pm and Thursday from 10 a.m. to 4 p.m. The Portland Public Library is closed for the holiday on Wednesday but will open as a cooling center Thursday from 10 a.m. to 6 pm. For more information about other cooling centers in the state, visit the Maine Emergency Management Agency website.

Essential city services, like trash pickup, are planned to continue on as normal, according to Jessica Grondin, Portland’s communications director.