Warnings Issued as Saturday Heat Expected to Top 100 F In Much of US

New York City faces “potentially dangerous heat” tomorrow as high humidity combines with temperatures near 100 degrees Fahrenheit, while another round of damaging thunderstorms may strike Washington and the U.S. mid-Atlantic region.

Temperatures across New York City are expected to range from 98 to 101, which may feel as hot as 106 because of humidity, according to the National Weather Service in Upton, N.Y. An excessive heat watch and a heat warning were posted for the area.

“Saturday is definitely looking like the worst day in terms of unhealthy heat,” Tim Morrin, a Weather Service meteorologist, said.

High temperatures boost demand for electricity as people turn to air conditioning to cool homes and businesses. That can increase electricity prices on the spot market and tax distribution networks, leading to power outages.

The heat may cause New York and much of the mid-Atlantic to use about 10 percent more electricity than normal to stay cool from July 7 to July 13, said David Salmon, owner of Weather Derivatives in Belton, Mo.

There is a slight risk of severe thunderstorms from Kentucky to the mid-Atlantic coast, including Washington, Richmond and Philadelphia, this weekend, according to the Storm Prediction Center in Norman, Okla.

“The main threat will be damaging wind with isolated hail possible,” according to the center.

Thousands throughout that region lost power when a wave of powerful thunderstorms crashed through last week, knocking down trees, grounding wires and damaging homes and buildings.

According to Weather Service bulletins, people living in New York and New Jersey face “potentially dangerous heat” and should limit working outdoors.

If the temperature reaches 100 in Central Park, it will be the first time that has happened in almost a year, according to the Weather Service’s website. Since 2001, the temperature has reached 100 in the park five times, once in 2001, twice in July 2010 and twice last year.

It would be the first time in 57 years the temperature has hit 100 in Central Park three years in a row, according to the Weather Service.

Morrin said the combination of high temperatures and humidity hinders the body’s ability to cool itself, making the weather feel hotter.

Heat is also affecting much of the eastern U.S.

“Very intense hot weather continues in the short range for the Midwest, Deep South, and East with more record high temperatures probably in many spots into this weekend,” said Matt Rogers, president of Commodity Weather Group LLC in Bethesda, Md.

Washington is expected to reach 100 today and 101 tomorrow, according to the Weather Service. Baltimore may peak at 103 tomorrow, with Philadelphia reaching 102 and Richmond registering 103.

Excessive heat warnings have been issued across the Midwest from the Great Lakes to southern Missouri, Chicago is forecast to reach 102 today, while the high in Des Moines, Iowa, may be 102 and St. Louis may be 109 today and 110 tomorrow, according to the Weather Service.

The heat is expected to reach into New England and southern Canada, as well.

Boston’s high may be 95 tomorrow. Toronto is forecast to reach 97 today and Ottawa 91, according to Environment Canada.

Since July 1, at least 1,215 daily high temperature records have been set or tied across the U.S., according to the National Climatic Data Center in Asheville, N.C. The highest temperature this month was 112 in Tennessee.

Temperatures along the East Coast are expected to cool next week, Morrin said.

Rogers said seasonal temperatures should blanket the region from Ohio to Maine, while it may be cooler than normal from North Carolina to Florida for July 11 to July 15.

There is potential for heat to return from July 16 to July 20 with temperatures rising to about 5 degrees above normal across the northern U.S. and 8 degrees above normal in Canada.

For July 10, the normal average temperature in New York City is 77, according to MDA EarthSat Weather in Gaithersburg, Md. It’s 73 in Boston; 80 in Washington; 80 in Atlanta; 75 in Chicago; 84 in Houston; 65 in Seattle and 74 in Burbank, Calif.