Scott Barr, Pelle Edberg, Christian Nilsson, Gary Murphy and Jeev Milkha Singh also shot 64 at the tournament, reduced to 54 holes after rain washed out play Thursday.
Wiegele eagled the par-5 15th hole to take the lead, but finished with two straight bogeys.
Until then, it was a dream round, he said. A shame that my finish wasnt perfect.
Paul Lawrie shot 68, Michael Campbell shot 69 and Darren Clark 70. Defending champion Richard Green shot 71.
Heavy rain was forecast for the weekend.