Kerry Wood (2-0) struck out at least one in each of his eight innings of work, eventually striking out 13 and then watching Joe Borowski fan a 14th for his second save.
The Pirates never had more than one on base in any inning against Wood.
Five of Wood's strikeouts came on called third strikes as he worked the corners not only with his fastball but with a breaking ball that froze the already blue-lipped Pirates.
"His breaking ball is a special thing on most days," Cubs manager Dusty Baker said, mentioning Wood in the same context as some of the all-time great power pitchers. "Everybody talks about Nolan Ryan's fastball and Sandy Koufax's fastball. But the special thing was their breaking ball.
"When Kerry Wood's breaking ball is over, it makes him extremely tough to hit."
Wood struck out at least 10 for the 27th time in his career. He said he felt good despite the cold and that he made an effort to keep the game moving for his fielders and the parka-clad crowd.
"I was throwing strikes and getting ahead of guys," he said. "And when you get ahead, you want to come back on them and make the next pitch."
Wood did walk four batters, which pushed his pitch count to 122. That was beyond the number Baker would allow in a game played in 42-degree temperatures, with an additional chill from a constant wind that snapped the flags all afternoon.
The Cubs ended the near-flawless season of Pittsburgh starter Kris Benson (2-1) in the second inning when Corey Patterson's two-out double and Mark Bellhorn's single scored the first earned run Benson had allowed in 141/3 innings.
Damian Miller added a second run when he led off the third with a ferocious line drive into the teeth of a 20 m.p.h. wind that landed in the first rows of the left-field bleachers for his second home run of the season.
Teammates were teasing Miller afterward about his newfound power. Both of his homers have been hit directly into a stiff wind.
"If they want to give me a hard time about that, I'll take it," Miller said, laughing.
The Cubs added two more runs with help from the Pirates in the bottom of the seventh.
Right fielder Kevin Young went to the base of the wall for Patterson's fly ball but dropped it when the wind caused the ball to fall short of the wall, putting Patterson at second.
Patterson then stole third without a throw when Benson failed to check him before delivering his pitch.
Miller drove Patterson across with a single, and Wood sacrificed Miller to second.
Mark Grudzielanek then hammered a one-hop single to right and Miller, running with two outs, was safe when Young's throw was slightly up the first-base line and catcher Jason Kendall was slow to get the tag down.