Chris DiMarco moved to the top of the leaderboard before bad light stopped play at the Zurich Classic in New Orleans.
DiMarco, who was runner-up in the Masters last month, sunk four birdies in 10 holes in the rain-delayed third round to move to 12 under par.
Rain held up the start of play until late in the morning, and only 15 golfers had finished their penultimate round when play was halted.
James Driscoll had played 11 holes and was one shot behind DiMarco, while second-round leader Arjun Atwal of India was another shot further back, having also completed 10 holes.
Ireland's Padraig Harrington is tied in seventh place on -8.