The Scot, bidding for his fourth Senior Major Championship and first on British soil, completed 12 holes before the suspension, twice leading outright on six under par before bogeys on the tenth and 12th holes, either side of a birdie on the 11th, pushed him back to five under par, alongside seven other players.
With constant rainfall throughout the morning, play was suspended at 1pm with the greens on the Old Course waterlogged. Further heavy rain after the suspension, and a worsening forecast, meant the decision was then taken at 3pm that the players would not return to the course, with 16mm of rainfall already measured at that point.
It means the second round will resume at 8am on Saturday morning, followed by a two-tee start for round three upon its conclusion.
David Williams, championship director, said: “We were looking at the weather forecast and giving it a little bit of a chance, but it did not improve and was deteriorating for the afternoon. The course was getting more and more flooded, and with the forecast, there was no chance of improving whatsoever to get out again.
“The plan is to finish round two tomorrow and, all going well, start round three on a two-tee start. We will have probably an hour or so play left of round three tomorrow, and we’ll finish that up on Sunday morning. Then the plan is to go three-balls off one tee and get back on track and finish when we’re meant to.”
Montgomerie will have six holes to complete when the play resumes on Saturday, having moved up the leaderboard to join the cluster of pacesetters.
The 2010 European Ryder Cup captain birdied the par five first for the second day in succession, and followed it up with another at the third.
A delightful close approach to the fifth meant he gained another shot, and his fourth birdie came on the 11th, but that was sandwiched in between those two bogeys, meaning he left the course two under par for the round.
Seven other players also lie on five under par, including defending champion Bernhard Langer and Spaniard Miguel Angel Jiménez, though only one of them, American Bart Bryant, has started his second round, parring the first two holes before the rain made the saturated greens unplayable.
China’s Lianwei Zhang, who had been part of the record eight-way tie for the lead after the first round, dropped to four under par. He birdied the first hole to take the outright lead but followed it with a costly double bogey at the second, then mixed two more birdies with two bogeys to be one over par for the round through nine holes.
Former Masters champion Ian Woosnam looked to be making the most significant move, eagling the first on his way to a front nine of 31, to move to four under par for his round and five under par overall.
Like Montgomerie, however, the Welshman bogeyed both the tenth and the 12th holes to drop back to three under par.
Of those to complete their rounds, America’s Gary Rusnak and Uruguay’s Cesar Monasterio share the clubhouse lead on two under par, with Steve Jones among those one shot further back, having now played the first hole in five under par through two rounds after a second round eagle followed his first round albatross.