The game will be made up on July 14 beginning at 2:20 EDT. July 14 originally was a day off for both teams.
Chicago's Greg Maddux (0-1) and Pittsburgh's Mark Redman (1-1), Friday's scheduled starters, will pitch Saturday. Kerry Wood (0-1) will face Josh Fogg (1-1) Sunday.
Pirates left-hander Dave Williams, originally scheduled to start Saturday, will be pushed back to Monday against Houston at PNC Park.
"I like the way Fogg pitches in this ballpark (Wrigley Field) and Dave Williams has had some success against Houston," Pittsburgh manager Lloyd McClendon said.
Cubs manager Dusty Baker inserted Jose Macias into the lineup at third base for Aramis Ramirez, who has had groin problems in the past.
"He's OK," Baker said. "I just didn't want to take a chance with the field conditions."