With temperatures expected to top 90 degrees Fahrenheit (32 Celsius) all week, U.S. Northeast utilities urged customers to conserve electricity so there would be enough energy to power everyone's air conditioner.

"Our system is performing well. We'll keep putting the message out for customers to use energy wisely. It's going to be hot out there and we're ready," said Mike Clendenin of Consolidated Edison Inc. , which serves 9 million people in the New York metropolitan area.

Electricity demand typically peaks during the summer, when air conditioning accounts for about a third of all power used.

Officials at the regional grid operators, serving 60 million people from Maine to Virginia, however, have warned the loss of a major transmission line or power plant during a heat wave could trigger brief, local brownouts or blackouts, especially when power supplies are tight.

Power supplies in New York City and its suburbs on Long Island, as well as in Connecticut, are some of the tightest in the nation because construction of power plants and transmission lines has not kept up with the region's economic and population growth.

Meteorologists forecast the mercury would rise to 96-97 F (36 C) in New York City on Monday and Tuesday, with a heat index, which combines the effect of the heat and humidity, making it feel closer to 105 F (40 C).

Despite the heat, the New York ISO, which runs the power grid for more than 19 million New Yorkers, does not expect any electricity demand records to be broken.

The peak load forecast in New York State for Monday is just over 29,200 megawatts (MW), well below the state's record peak of 30,963 MW set Aug 9, 2001. There are close to 36,000 MW of power supplies available in New York.

One megawatt is enough energy to power about 1,000 homes.

It will be hot and humid everywhere east of the Mississippi with temperatures in the Mid-Atlantic and New England states reaching 94-96 F (34-36 C), with a heat index similar to that of New York -- near 105 F (40 C) -- on Monday and Tuesday.

Grid operators in New England and the Mid-Atlantic states also expect the hot and humid weather to push electric demand to near record levels.

While the heat will continue all week, meteorologist said the humidity is expected to break late Tuesday when the heat index dips to the low-90s F (low-30s C).