CHICAGO - Forget temperature and humidity readings. Walk into the shower room of a health club sometime when every stall is blasting hot water. Then put on a baseball uniform and try to retire a major league lineup. That was Roy Halladay last night at Wrigley Field.

The veteran righthander lasted less than five innings in the thick blanket of heat and humidity that swallowed the Windy City, allowing three runs in four-plus innings before watching the rest of the Phillies' 6-1 loss to the Cubs from the clubhouse.

Halladay, who is renowned for his physical conditioning, never looked like himself. He allowed a solo home run to Aramis Ramirez in the first inning, then threw 31 pitches as the Cubs added a couple of runs in the third. At one point during that inning, Halladay bent over in exhaustion. Before taking the mound in the fourth, he took off the red, three-quarter-sleeve undershirt he usually wears beneath his jersey. He would last just one more inning.

After allowing a leadoff single to Starlin Castro to start the fifth inning, Halladay bent over, prompting head athletic trainer Scott Sheridan to head to the mound. After a brief conversation, Halladay left the game. It was his shortest outing since June 12, 2009 with Toronto, when a groin injury limited him to three innings against Tampa Bay. Until last night, Halladay had made 63 consecutive starts of six innings or more on the road, the longest streak in the majors since Walter Johnson logged 82 straight from 1911-15.

Halladay was not available to speak to reporters last night, but told a Phillies spokesman to relay a message: He "absolutely" will make his next start, which at the moment is scheduled for this weekend against the Padres.

"He was battling," manager Charlie Manuel said. "He got real hot. He kind of got dizzy. We were concerned about dehydration."

The temperature at gametime was 91 degrees, with damp air that only made the heat feel worse. Manuel said he never has seen Halladay struggle with the heat before. He also said Halladay did not exhibit any symptoms before the game.

"We played in Washington earlier this year, and he pitched, and it was maybe hotter there," Manuel said. "The humidity might have been a little worse today, but it was 103 there."

Cubs righthander Rodrigo Lopez, who spent a stint with the Phillies in 2009, allowed one run on five hits in 6 innings, striking out three and walking none. The Phillies got their only run in the fourth inning when Jimmy Rollins homered to right-centerfield. It was the shortstop's ninth homer of the season.

The only other extra-base hit was a double by John Mayberry Jr., who went 2-for-4. Ryan Howard went 0-for-4 with a strikeout and saw his average dip to .249. He is 1-for-15 since the All-Star break.

The Phillies are now 59-36 and lead Atlanta in the NL East by 2 after the Braves' victory in Colorado.

Halladay, who was making his first start since logging two innings in the All-Star Game, is 11-4 with a 2.57 ERA.

It isn't getting any cooler this week. Temperatures for tomorrow's afternoon matchup between Vance Worley and Ryan Dempster are expected to be in the mid-to-upper 90's.

"They aren't going to call the game off because of heat,'' Manuel said. "I've seen it 125 [degrees], 130 [degrees]. We're going to have to play. They've got to play too.''

For more Phillies coverage and opinion, read David Murphy's blog, High Cheese, at www.philly.com/HighCheese. Follow him on Twitter at http://twitter.com/HighCheese.