When the temperature goes up, business goes down for Kingsley Horton's lunch truck, and this has been a particularly bad week.

A stubborn and dangerous heat wave (search) that sizzled across the West and Midwest for days lingered in the East on Wednesday with hot, humid air keeping workers in their air-conditioned office towers and only the delivery crews out on the scorching streets.

"Street vendors really don't do well when the weather is this hot," said Horton, 49, whose customers appeared to be heeding the advice of health experts to stay out of the heat. Demand for electricity to run air conditioners and fans shot up in at least nine states.

Even those wearing shorts — and driving around with open doors — couldn't escape the heat, as UPS driver Hugh Kovacs could attest.

"I drink tons and tons of water, I wear a wet towel around my neck when I drive and just deal with it," said Kovacs, 43, after making a delivery to a convenience store in Northfield, N.J.

Relief in the form of a cold front bringing temperatures in the 70s and 80s was expected to reach the East Coast on Thursday, but Wednesday felt anything but promising as temperatures soared into the upper 90s for a fourth straight day.

Heat warnings and advisories were in effect Wednesday for the District of Columbia, Virginia, North and South Carolina, New Jersey, Maryland, Delaware, and parts of Pennsylvania, New York and Georgia, the National Weather Service said.

In Richmond, Va., a country music radio station began playing Christmas carols to remind listeners of more comfortable days.

"The phones just went bananas," said Jim Tice, program director at WKHK. "People really appreciated the cooling effect."

The Navy even closed the USS Wisconsin (search), a battleship on display to the public in Norfolk, Va., when the temperature on the warship's deck hit 120 degrees.

One place business was booming: water parks.

"The heat is definitely driving people to the water," said Emily Ball, manager at Wild River Country in North Little Rock, Ark.

The weather also caused another spike in demand for electricity.

In New York, Consolidated Edison (search) reported a record high for electricity use as customers cranked up air conditioners. The power company, which serves the city and suburban Westchester County, said its customers used 13,059 megawatts at 5 p.m. Wednesday, eclipsing the previous record of 12,551 megawatts set Tuesday.

A day after transmitting the world's largest-ever electric load, regional power grid operator PJM Interconnection asked electric customers in the Mid-Atlantic region to conserve energy Wednesday.

The heat has been blamed for at least 29 deaths in the Phoenix area, most of them homeless people, along with at least four in Missouri, two in New Jersey, two young children left in hot cars in Oklahoma, and one each in Kentucky, Ohio and Mississippi.

The heat also was blamed for at least 1,200 cattle deaths in Nebraska.

Farmers across the Midwest have used everything from electric fans to cold showers to protect their livestock from the oppressive heat.

Tracy Swank, who raises sheep near Toledo, Ohio, said she has been opening more barn doors to increase air flow and filling more troughs and buckets with water.

"Animals are pretty resilient. They'll adjust, but you still have to give them plenty of water and provide some shade," she said.