Via press release from the Cubs:
This afternoon’s game between the Chicago Cubs and San Francisco Giants at Wrigley Field has been postponed due to the forecast for inclement weather and poor conditions throughout the day.
The decision to postpone today's game was made in consultation with the club’s weather service. Based on the current forecast, the Cubs feel it is better to err on the side of caution and postpone the game at this early hour before the gates open.
A make-up date for this afternoon’s postponement has yet to be established. Fans should retain their tickets from this afternoon’s game to be used for the rescheduled contest. Fans can visit www.cubs.com for updated information when it is available.
The Cubs made the right call. Although it's not raining at this moment, it looks like it will off and on all afternoon, and the winds are howling. This, again, is likely the reason they played last night through awful conditions, because they figured they might have to postpone today's game and didn't want to have to try to reschedule two games.
Maybe by the time the Cubs get back from their road trip to Cincinnati, Florida and Boston, it will be a little nicer weatherwise in Chicago. I wouldn't count on that, though.