The 2007 Masters Tournament champion shot 10-under 60 in the rain-delayed event to take the clubhouse lead at 12-under 195.
Second-round leader Paul Goydos and Justin Leonard were also 12-under for the tournament through 12 holes when play was suspended by darkness.
Johnson holed out from 84 yards for an eagle on the par-4 seventh and had eight birdies on the soggy course in the round interrupted by a five-hour rain delay.
Johnson, who started the day tied for 18th place and three shots off the lead, birdied the 17th hole to go to 10-under on the par-70 course.
He hit his approach shot on No. 18 to within 20 feet of the hole.
The small gallery, thinned out the by lengthy delay and encroaching twilight, groaned when he came up 2 feet short.
"I did not want to leave that putt short," Johnson said. "But, whatever, it was nearly pitch black."
Evans resident Vaughn Taylor shot 69 and is at 207.
LPGA TOUR: In Clifton, N.J., Suzann Pettersen and Ji Young Oh seemingly won't have to worry about three-time defending champion Lorena Ochoa making a run at them in the final round of the Sybase Classic.
Pettersen and Oh shot 3-under-par 69s on Saturday, taking a one-stroke lead over Brittany Lincicome after three rounds of the LPGA Sybase Classic.
Ochoa is 10 shots off the lead after 72.
Pettersen and Oh have 54-hole totals of 12-under 204.
There are plenty of other challengers though, including recent major winner Lincicome, eight-time LPGA winner Paul Creamer and probably the most famous non-winner on tour, 19-year-old Michelle Wie.
Lincicome shot 72 after entering the third round ahead by two strokes while Creamer and Wie had 68s and are three back.
The biggest story would be Wie winning her first title since the USGA Women's Amateur Public Links in 2003.
CHAMPIONS TOUR: In Hoover, Ala., Gene Jones and Keith Fergus were in the lead at 10-under for the tournament when play was suspended by rain in the second round of the Regions Charity Classic.
Jones was 7-under through 14 holes in his second round. Fergus had finished the front nine in 4-under to join him atop the leaderboard.
Augusta native Larry Mize was 1-under through nine holes in the round and 7-under for the tournament.
Augusta native Jim Dent was 1-over through 13 holes and 2-over for the event.
EUROPEAN TOUR : In Baltray, Ireland, amateur Shane Lowry bogeyed the final hole to fall into a tie for the lead with England's Robert Rock after three rounds of the Irish Open.
Johan Edfors had 68 for the day's best round and was two strokes behind.
Former Augusta State player Oliver Wilson had 76 after opening with 66-68. Wilson, who had five bogeys and one birdie in the third round, is 10 shots off the lead. Gary Murphy, another former Jaguar, had 75 and is 14 back.
NATIONWIDE TOUR: Australia's Michael Sim shot 9-under-par 62 at Thornblade Club in Greer, S.C., to take a three-shot lead in the BMW Charity Pro-Am.
Sim, the tour's leading money winner by more than $90,000, is at 20-under 195. He has a victory and a playoff loss in the past two events.
Three of the eight golfers with area ties made the 54-hole cut in the event, which played three different courses.
Scott Brown (68 on Saturday) is 11 shots back at 206, Scott Parel (74) is at 207 and Matt Hendrix (68) made the cut on the number at 208.
Major Manning (71) finished at 210, David Robinson (72) had 212, Stephen Poole (72) and Kevin Kisner (68) finished at 214 and Richard Johnson (77) had 219.
HOOTERS TOUR: In Edwardsville, Ill., Kelly Grunewald shot 1-over-par 73 but still has a two-shot lead in the Sunset Hills NGA Classic.
Grunewald, who opened with a pair of 68s, is at 7-under 209. Luke List (68) and Bronson La Cossie (72) are tied for second.
Augusta Emmett Turner, a first-round co-leader after 67, followed that with 77-75 and is nine shots off the lead.