Temperatures soared toward 100 degrees or more Tuesday along much of the East Coast, sending utilities into peak operation as air conditioners strained to cool the sweating masses and sending the unlucky into cooling centers or anywhere else they could beat the heat.

After an extended Fourth of July weekend when temperatures inched into at least the 90s from Maine to Texas, The National Weather Service issued heat advisories until 11 p.m. Wednesday for much of the Northeast, mid-Atlantic and parts of Michigan and Kentucky. Wednesday was forecast to be the most humid day ofthe stretch.

The heat was expected to put a heavy load on the power grid. Utilities in New York and Philadelphia could break records for electricity use, spokesmen said. Utility workers in New York and Westchester County were working 12-hour shifts because of the increased demand.

In Philadelphia, the increased load from the heat blew fuses at transformers run by the Peco utility, said spokeswoman Karen Muldoon Geus. About 8,000 customers lost power, but it was restored Tuesday.

Those without air conditioning were left to cope as they could.

In the Bronx, Gardenia Childs, 72, walked to the store early and bought herself an extra fan, but swore off any more exercise for the day as she wheeled it home in ashopping cart.