At 6:35, the tarp was off the field. Roger Bossard was being interviewed on Comcast, saying they were going to play through the wet weather. But when they came back from commercial just after 7, the tarp was back while Hawk and DJ talked of double headers and rain outs. By 8 PM, they had called the game.

The Sox are scheduled to make up the game as a true double header tomorrow, so you halfway to St. Patty's ticket holders are pretty much out of luck. I'm sure the Sox would rather have a split double header, and not lose a game at the gate, but FOX was scheduled to broadcast the game so the first game doesn't start until nearly 3 PM.
I don't think it will matter much. I'm no meteorologist, but based on the weather report for tomorrow, I have trouble seeing them getting both games in. They might be able to get one in, playing through a number of delays, but I don't think they'll get two.
MLB was busy friday night, postponing 6 games total, including the Twins-Orioles game. The Twins are also scheduled for a double header tomorrow, so it's not like they gain any advantage by getting to keep their starters on regular rest while the Sox scramble.
The remnants of Hurricane Ike are supposed to over southern Chicago at game time on Sunday, which is a night game on ESPN. Because of the national broadcast, I doubt they'd move that up to, say, noon just to get the game in. If they're only able to get one game in tomorrow, baseball should step in and send the game to Milwaukee, as has been discussed for the displaced Cubs.
Speaking of the Sox rotation, it would be fool hardy to try to hazard another guess based upon the approaching weather patterns, but I'm going to do it anyways. John Danks and Javier Vazquez are scheduled to throw Saturday, with Vazquez working on short rest. Friday's rainout would force Danks to come back on short rest, not just once, but twice in a row, if the Sox wish to keep their rotation as I outlined a couple days ago. I highly doubt they'd do that to a pitcher who has appeared tired for much of the last month.
Keeping Danks on regular rest by giving Clayton Richard a start in the Yankees series would also prove to be a sub-optimal solution, as each of the three starters in the Twins series would need to be on short rest. In other words, the Sox are screwed. We're either going to see 3 more starts by the 5th starters or the starters pushed to go on short rest multiple times before season's end.
[Note by Christopher Michaels, 09/13/08 11:29 AM CDT]: Larry notes that I should probably read the articles to which I link. Danks will not pitch today (though right now it doesn't seem like anyone will) and will go Sunday instead. Vazquez and (probably) Broadway are scheduled to throw today. The point remains, the Sox rotation plans are out the window.