For the second day in a row, temperature hit the 100-degree mark in the Philadelphia region, with the heat contributing to the death of a 67-year-old Germantown man, according to the city health department.

There were scattered minor power outages, a racetrack closing, and increased water usage as the National Weather Service extended its excessive heat warning until Sunday at 8 p.m. It had been set to expire Saturday night.

The 100-degree mark, reached around 3 p.m., topped the old record for July 23 of 99 degrees, set in 1978 and 1999. The heat index popped up to 110 Saturday.

Walker Ferguson, 62, of Germantown, acknowledged the heat as he sat outside the Reading Terminal Market playing the blues on his electric guitar and throwing in a few melody lines with a harmonica.

Like a true bluesman, though, he said, "We can complain a lot about anything, but we can't do nothing about it but accept it."

Ferguson reasoned that "the creator gave us the heat and I'm going to enjoy it." Besides, he said, "In the winter, we're going to be complaining about that."

Lower humidity made Saturday less unbearable than Friday.

The Germantown man, whose name was not released, was found in his residence Saturday afternoon. His windows were closed and he was not using air-conditioning, said Jeff Moran, a spokesman for the Philadelphia Department of Public Health. It was the fifth heat-related death this summer and the first attributed to the current heat wave. In addition to the high temperatures, cardiovascular disease also was a cause of death, Moran said.

Authorities in central Pennsylvania said two men died in York County of hyperthermia during the ongoing heat wave.

Lower humidity made Saturday less unbearable than Friday.

Still, because of the heat's danger to animals, Parx Racing in Bensalem canceled Saturday horse racing. Races probably will resume Sunday at 12:25 p.m. "but that all depends on the weather," said Jamie Houghton, a racing official.

A power outage knocked out air-conditioners at the Wilson Park apartments in South Philadelphia Saturday morning until early afternoon.

Many of the building's 287 seniors headed to the complex's community center for relief, according to police Capt. Lou Campione. The community center was unaffected by the outage in the building.

Ben Armstrong, a spokesman for PECO, said the outage was caused by the failure of some Philadelphia Housing Authority equipment. Power was restored about noon.

Armstrong said there also had been an outage affecting about 100 households in the area around 57th and Pentridge streets in West Philadelphia.

"The PECO system has held up very well during these extreme conditions," Armstrong said. "There have been a few scattered outages throughout the week."

PECO recorded record power usage on Thursday, he said, and may have topped that on Friday, but figures will not be available until Monday.

The massive power grid of which Philadelphia is only a part has also held up well during the extreme heat, according to Ray Dotter, a spokesman for PJM Interconnection, a regional transmission organization that oversees wholesale electricity in all or parts of 13 states and the District of Columbia.

Dotter said the entire system saw record demand on Thursday. A new line bringing an extra 1,000 megawatts of power to the I-95 corridor helped meet demand from Virginia to Philadelphia, he said. The line has been functioning since May.

Dotter also cited a program of voluntary reductions by large users that has freed up a considerable amount of power during peak periods.

"That gave us enough headroom," Dotter said.

PJM is the largest grid in North America and represents the fifth largest consumer of electricity in the world, he said.

Both PECO and PJM officials said that demands on the power grid should be less over the weekend because of closed business and manufacturing facilities. Even so, "demand will be very high for any day," said Dotter.

"The system is at greater risk at periods of high demand because you have less flexibility," he said. "But we drill. We have simulators. Several times a year we go through scenarios of what could go wrong. So that when the real thing happens, we've practiced it."

The weather service said the heat warning is in effect for the entire Philadelphia region, stretching from Trenton to New Castle, Del.

Urban areas probably won't see a cooling off lower than 80 degrees tonight.

There may be showers and thunderstorms Sunday or Monday.

Despite the excessive heat, suburban water officials said no use restrictions have been imposed because all area reservoirs entered the summer at full capacity.

"Thanks to higher-than-average rainfall this spring, our five reservoirs in Southeastern Pennsylvania entered the summer . . . with approximately 10 billion gallons of water," said Aqua America chairman and chief executive Nicholas DeBenedictis. "Now, despite a week of record temperatures and peak water demands, our reservoirs are currently at 95 percent capacity."

Aqua reported usage of 144 million gallons on Thursday, an Aqua spokeswoman said Saturday, adding that heavy usage at peak times could result in a temporary drop in water pressure.

SEPTA officials said that the heat has caused no major system problems. But for riders stuck in a train car or a bus without air-conditioning, that's a small comfort.

Gerri Williams, SEPTA spokeswoman, said that about 20 buses and five or six train cars have had problems with air-conditioning in the last few days.

"Every day we do a check," she said, and if an air-conditioning problem is found, the car is taken out of service. Nevertheless, she acknowledged, the air-conditioning breaks down. The bus, subway or rail car is removed from service and repaired, she said.

As far as the overall SEPTA power system is concerned, heat by itself is not the issue. Problems are far more likely to develop when there are rapid temperature changes.

"It's been a heat wave," she said, not a sudden, drastic increase of heat. Hot is hot for the wires."

With a couple of notable exceptions, roadways have held up fairly well under the searing sun, according to PennDot officials.

Gene Blaum, PennDot spokesman, said that "with very oppressive heat over a number of successive days, it's not uncommon" to see roads begin to crack.

Route 422 near Royersford in Montgomery County buckled in both directions on Friday. One lane closed eastbound during the afternoon, then a westbound lane buckled in the evening. All lanes in both directions were open by 11 Friday night.

Earlier in the week, the southbound off-ramp from the Commodore Barry Bridge to I95 in Chester experienced a similar problem.

It happens, said Blaum, with "older concrete pavement."

Jim Lardear, director of public affairs for AAA Mid-Atlantic, said a similar problem occurred during the week on Route 1 in Delaware.

He added that AAA is "already seeing" an uptick in calls for roadside assistance. Hot weather means hot and hotter engines. In addition, "batteries die more in the heat than they do in the winter," he said, largely because of the heavier demands placed on them.

"For the AAA Mid-Atlantic, roadside assistance calls can increase by about 700 per day when we reach extreme heat on days like today," Lardear said in an e-mail Saturday.

The potentially lethal mix of a prolonged period of heat and high humidity can cause heat stroke and exhaustion, the weather service said. People should drink plenty of liquids, stay out of the sun and check on friends and neighbors, particularly the elderly.

The Philadelphia Corporation for Aging extended operation of its heatline through 8 p.m. Sunday. The number is 215-765-9040 and is open to people of all ages seeking advice on heat related problems.

Marcia Z. Siegal, PCA public relations manager, said trained staffers are manning the phones. On Wednesday, the heatline received 101 calls and seven people were referred to city Health Department nurses. On Thursday, there were 234 calls and nine were referred to nurses. Final figures for more recent days won't be compiled until Monday.

"The calls have really been picking up and there have been more referrals to the nurses," Siegal said Saturday. "As the heat is building, people are experiencing more problems."

Inquirer staff photographer Chip Fox contributed to this article.