(CBS News) — The dangerous heat wave scorching much of the country has turned deadly and more than 103 million Americans are under heat alerts.

Three people have died due to the heat in the Northeast — two in New York and one person in Pennsylvania.

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The extreme heat will blanket a huge section of the country Wednesday, stretching from the Midwest into the Northeast. High temperatures are expected to soar into the 90s in many cities and it will feel like triple-digit heat in places like Louisville, Charleston and Charlottesville, Virginia.

Officials are warning people to stay hydrated and alert, reports CBS News’ Jericka Duncan from Jones Beach, New York. This has been the hottest stretch in the region since 2013.

Hundreds of people in Boston sat under the hot sun through temperatures that reached the mid-90’s to watch a pre-holiday concert. The heat index made it feel closer to 105, so fans took precautions.

In Addison, Texas, just north of Dallas, at least three people attending a holiday festival were taken to the hospital for heat-related emergencies. Many others were treated on the scene and released.

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In New York, volunteers with Meals On Wheels deliver 18,000 meals every day, making a point to knock on doors, especially during extreme weather like this.

During this ultra-hot stretch, they are paying even closer attention to how the heat is affecting the elderly. The city’s Office of Emergency Management says seniors are one of the groups at increased risk of heat-related health issues.

Two other deaths that may be heat-related are being investigated in Kansas City.

Many people are going to city pools or beaches to try to stay cool. Officials told CBS News more than half a million people have flocked to Jones Beach alone since the heatwave started.

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