Patrick was to have taken part in qualifying Friday for Saturday's Nationwide race. Instead, she was assigned the No. 15 starting position for her first NASCAR appearance.
Because qualifying was wiped out, the starting grid was determined by owner points from the 2009 season.
Patrick finished sixth in the ARCA race held at Daytona last weekend and, based on that showing, she decided to make her Nationwide debut this week.
"I think that I'm just gonna have to stay calm and cool," said Patrick, who has won once in her Indy Car career. "If the car is difficult to drive, I think the discipline will be to just keep it at the pace that I'm comfortable with, keep it in the race, try and work on it on the pit stops and tune it in as much as possible."
Kyle Busch will start on the pole for the 300-mile race, followed by Carl Edwards, Dale Earnhardt Jr., Kevin Harvick and John Wes Townley.
The season-opening event in the Camping World Truck Series was also rained out and was rescheduled for Saturday.