Long Islanders might want to head straight for the beach Sunday to get a little relief from will be a very hot and humid day, forecasters said.

Conditions have prompted an air-quality alert until evening for young children, people with heart problems and those with asthma.

"It'll be hazy, hot and humid and not a good day for people with respiratory problems or anyone especially sensitive to elevated pollutants," Pat Cavlin, a meteorologist with News 12 Long Island, said.

The sun will be out for most of the day with a high of about 89, but there is a slight chance of an isolated thunderstorm Sunday evening, when the low will be around 73 degrees with continued muggy conditions, Cavlin said. "There's a very slight chance of a thunderstorm -- if anything, there may be something around dinner time."

Faye Barthold, a meteorologist for the National Weather Service in Upton, said Long Island is entering the warmest part of its summer. "Mid- to late July tends to be the warmest period and with it comes an afternoon thunderstorm with the warming of the day," Barthold said.

For the start of the workweek on Monday, look for another hazy, hot and humid day with temperatures climbing to a high near 90. It will be mostly sunny but a chance of a thunderstorm will come in the afternoon, most likely between 4 and 7 p.m., Cavlin said. The low Monday night will be about 70.

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Tuesday will bring another hot day, with high humidity and a high around 88. he said. Skies will be partly sunny and the muggy conditions continue again into the evening, when temperatures again will dip to around 70.

Relief comes Wednesday, when better breathing weather returns, Cavlin said. "Finally, that's when the humidity breaks -- it'll be much better." He said the high will be around 85 and there will be a mix of sun and clouds. The low will be near 67.

On Thursday the high will be down to around 84 and it will be mostly sunny with low humidity. Look for a low of about 67.

The start of the weekend on Friday is expected to be sunny, with a high around 80, Cavlin said.

"Toward the Twin Forks, it'll be a little cooler," he said.