Cities that opened cooling centers this week advised that Wednesday’s Juneteenth holiday means some public libraries, senior centers and pools where residents could beat the heat will be closed.

The dangerous temperatures were expected to peak in the eastern Great Lakes and New England on Wednesday and Thursday, and in the Ohio Valley and Mid-Atlantic on Friday and Saturday, the National Weather Service said. Heat index readings were expected to reach 100 to 105 degrees (37.7 C to 40.5 C) in many locations.

People and even zoo animals were forced to find ways to thwart the muggy weather.

An organization that provides produce to areas with limited access to fresh food in Columbus, Ohio, prepared frozen towels and packed cold water for their workers.

“Hydration is the key,” said Monique McCoy, market manager for the Local Matters Veggie Van.

In Toledo, Ohio, the city canceled a weekly fitness event and a neighboring suburb called off a street fair as temperatures reached the mid-90s (about 35 C). A food bank in upstate New York canceled deliveries for Wednesday out of concern for staff and volunteers.

Schools in New York canceled field trips Tuesday to the Rosamond Gifford Zoo in Syracuse, where workers turned on water misters for visitors and the animals. Elephants and other animals were getting chunks of ice in their pools, said Ted Fox, the zoo’s executive director.

“Even the tigers love to lick the ice and put their heads on them when it’s this warm,” Fox said.

The blast of extreme temperatures came a little too early for many.

“This is hot for just moving in to summer, so I’m hoping that we’re going to see the downward trend in the temperature here soon because this is a warm one,” said Krista Voltolini, who was selling produce at a farmer’s market in Columbus.

A recent study found that climate change is making heat waves move more slowly and affect more people for a longer time. Last year, the U.S. saw the most heat waves — abnormally hot weather lasting more than two days — since 1936.

Chicago broke a 1957 temperature record Monday with a high of 97 degrees (36.1 C). Wednesday will be another hot day, but a cold front will bring relief to areas near Lake Michigan on Thursday and Friday, the National Weather Service in Chicago said.

That relief won’t come in time for the closure of all but one cooling center in Chicago on the Juneteenth holiday.

“It’s extremely alarming that we are shrinking our cooling centers in the middle of a heat wave,” state Rep. Lindsey LaPointe told The Chicago Sun-Times. LaPointe represents Chicago’s Northwest Side and advocates for people who do not have permanent shelter and other vulnerable populations.

Officials have urged people to limit outdoor activities when possible and to check in with family members and neighbors who may be vulnerable to the heat.

In New York, Gov. Kathy Hochul activated the National Guard to assist in any heat emergencies that develop over the next several days. She also said admission and parking fees at state parks, pools and beaches would be waived on Wednesday and Thursday.

“This is a time of significant risk, and we’re doing our best to make sure that all lives are protected,” Hochul said Tuesday.

In California, wildfires erupted east of San Francisco in the state’s historic Gold Country region and in the mountains of northern Los Angeles County after what had been a quiet start to fire season. Wildfires in southern New Mexico damaged 500 buildings Tuesday in a mountain village of 7,000 people that had been evacuated with little time to spare.

Meanwhile, a fresh batch of tropical moisture was bringing an increasing threat of heavy rain and flash flooding to the central Gulf Coast. Hurricane season this year is forecast to be among the most active in recent memory.