The game was suspended because of Rule 4.12 (a) (5)
A game shall become a suspended game that must be completed at a future date if the game is terminated for any of the following reasons: ...
Weather, if a regulation game is called while an inning is in progress and before the inning is completed, and the visiting team has scored one or more runs to take the lead, and the home team has not retaken the lead;
The Cubs trailed 5-2 going into the 7th then rallied for four on RBI doubles by Matt Murton and Alfonso Soriano and a 2-run home run by Cliff Floyd. The game should resume Wednesday afternoon at 9:35 am PT, followed by the regularly scheduled game.
Milwaukee and Florida had a suspended game that started on April 10 and finished on April 11 with the Brewers winning 3-2.
It is the first suspended game for the Pirates since June 16, 1986. And when that game was halted by rain with 2 outs in the top of the 6th, the umpires ruled the game over and gave the Cardinals a 4-1 win. The Pirates protested that the umpires did not wait long enough for the rain to let up and NL president Chub Feeney agreed and the game was restarted the next day. The Cardinals would win 4-2. It is the last protest to be upheld in MLB history.
The Cubs last suspended game was on April 5, 1997 in Atlanta. The Cubs were trailing the Braves 8-5 going to the bottom of the seventh when persistent rain showers forced the game to drag on past 12:45 am. Under NL rules of the time, any game stopped by rain after that time would be a suspended game.