After a record June heat wave peaked in Connecticut on Tuesday, the intense air temperatures and humidity will begin to subside on Wednesday, the National Weather Service said.
The stretch of hot weather officially became a heat wave on Tuesday when temperatures soared to just shy of 100 degrees in parts of Connecticut. A heat wave is defined in the Northeast as three or more consecutive days when temperatures are 90 or above.
Temperatures and humidity will begin to decline on Wednesday before the heat wave breaks on Thursday, the weather service said.
The heat wave was brought on by a heat dome, where high atmospheric pressure pushes down from the upper atmosphere, sending early summer temperatures soaring across the eastern U.S. As of Tuesday, nearly 89 million people were living in areas under heat alerts, according to heat.gov.
The weather service issued extreme heat warnings along the Atlantic seaboard from New England to North Carolina, while heat advisories stretch from eastern Texas to Georgia north to Illinois and northern Maine.
The heat appears to have sent people out to state parks and beaches, prompting closures as parks reached capacity on Sunday, Monday and Tuesday.
Nearly all of Connecticut remained under an extreme heat warning that was set to expire at 8 p.m. Tuesday, with the exception of northern Litchfield County and coastal New London County. Those areas were under heat advisories.
The heat wave tied a daily temperature record in Bridgeport on Sunday, then broke daily heat records in Hartford and Bridgeport on Monday. On Tuesday, the heat was forecasted to again break a daily heat record in Bridgeport and to challenge the highest temperature recorded in June at Bradley International Airport in Windsor Locks. That record — 100 degrees — was set in 1952 and 1964, according to weather service figures.
Heat index values, which measure the temperature when factoring in the humidity, was expected to soar to about 110 degrees Tuesday in parts of Connecticut, the weather service said.
Wednesday will be slightly cooler with high temperatures reaching the low- to mid-90s. Dew points in the 70s will mean the conditions will remain uncomfortably humid. Heat index values, , may still approach 100 degrees on Wednesday, the weather service said.
The southeastern Connecticut shoreline will remain a little cooler Wednesday with highs expected to stay in the 80s in some areas.
Temperatures fell just a few degrees short of 100 in Hartford on Monday. The high reached 98 degrees at Hartford-Brainard Airport and Bradley International Airport in Windsor Locks, setting a new daily record at both locations, the weather service said. Weather service records show 100-degree days in June are rare in Connecticut.
Heightened levels of ground-level ozone, a type of air pollution, were also expected to affect Connecticut on Tuesday, according to the state Department of Energy and Environmental Protection. Southern areas of the state east of New Haven to the Rhode Island state line are expected to see levels of ozone that are considered "unhealthy for sensitive groups."
Monday also saw heightened levels of ground-level ozone, which is common on hot sunny days. The pollution forms at ground level when pollutants from cars and other sources react with sunlight. It's the main component in smog, and can irritate the respiratory tract in people. The pollutant form of ozone is separate from the earth's naturally-occurring ozone layer in the upper atmosphere, which protects people from the sun's harmful rays.
"The heat continues through Wednesday, with Tuesday being the hottest day for many places," the weather service's New York office said.
"A slow-moving cold front approaches and settles nearby late Wednesday and into the latter half of the week," the office said. "The chances for unsettled weather increases with scattered showers and thunderstorms for late in the week."
After Wednesday, temperatures are expected to fall off dramatically, bringing an end to what will likely be a four-day heat wave.
Overnight lows Wednesday night will be in the 60s and low 70s, then Thursday will see highs only reach the 70s under mostly cloudy skies with scattered showers.