The BMW Championship was heading for a Monday finish after torrential rain swept across Conway Farms Golf Club on Sunday, forcing final-round play to be suspended for three-and-a-half hours.
With standing water affecting fairways and greens on the par-71 layout, the siren sounded at 10 a.m. CT (1500 GMT) to halt the action at the FedExCup playoff event after only 36 players in the field of 70 had teed off.
Play eventually resumed at 1:31 p.m. CT but with the final pairing of overnight leader Jim Furyk and second-placed Steve Stricker scheduled to start the final round at 4:10 p.m., there was no chance of the tournament ending on Sunday.
It will mark the third unscheduled Monday finish on the PGA Tour this year, the most since 2010 when three tournaments also spilled over into an extra day.
In all, 22 tournaments have been delayed by weather on the U.S. circuit this season, including the first three FedExCup playoff events.
Conditions are expected to remain cloudy and wet for the rest of Sunday, though the rain has been forecast to taper off later in the day.
Four players managed to complete their rounds, including defending champion Rory McIlroy who fired a second successive three-under-par 68 to finish at seven-over 291, having languished stone last after 36 holes.
That marked the end of McIlroy's 2013 PGA Tour campaign as he failed to qualify for the elite 30-man field for next week's Tour Championship in Atlanta, the final playoff event.
American Furyk, seeking his first PGA Tour victory since the Tour Championship in 2010 when he also landed FedExCup honours, was at 13-under 200 overnight after carding a two-under 69 in Saturday's third round.
Stricker was a further stroke back in second, having soared into contention with a 64, ahead of fellow Americans Brandt Snedeker (71), at 11 under, and Zach Johnson (69), at 10 under.
American world number one Tiger Woods, still smarting after being docked two strokes for a rules violation during Friday's second round, was a further shot back in fifth after returning a third-round 66.