The start of the sport's major championship season is set for 7:50 a.m. EDT Thursday, but forecasters said there was a 50 chance of thunderstorms in the area during the opening round.
Rain is also in the forecast for Friday, but conditions are expected to improve for the weekend.
A field of 96 players will compete over the historic course -- created by golfing legend Bobby Jones and the scene of some of the sport's most dramatic events.
This year's tournament has drawn special attention because of the recent PGA Tour victory produced by Tiger Woods, his first in more than two years. Woods will try to resume his chase of the career major championship record currently held by Jack Nicklaus.
Nicklaus won 18 majors in his career, the last coming on this course 26 years ago, and Woods needs four more to equal that mark.
McIlroy led after each of the first three rounds at the Masters a year ago, but suffered though a dismal closing-round 80 that left him in a tie for 15th place -- 10 shots off the winning score turned in by Charl Schwartzel.
McIlroy went on to win the U.S. Open and now stands among the likely challengers for this year's crown.
Three-time winner Phil Mickelson will be in the final threesome of the day, starting play at 12:53 p.m. with Hunter Mahan and Peter Hanson. Mahan, thanks to two victories on the tour this year, has climbed to No. 4 in the world and is the leading American in the rankings.