The Brewers won for the fifth time in six games and are just three games out of the second wild card spot in the National League. Atlanta, comfortably in front in the race for the No. 1 wild card position, fell 8 1/2 games behind Washington in the NL East pennant race.
Milwaukee sent 13 men to the plate in the fifth, an inning that began when Jeff Bianchi reached on a fielding error by third baseman Chipper Jones. That miscue eventually led to two of the eight runs being unearned.
In addition to the three-run homer by Weeks, the big inning was highlighted by a three-run double from Travis Ishikawa.
Yovani Gallardo (15-8) benefited from the outburst to win his seventh straight decision. He allowed two runs on four hits in seven innings.
All eight Milwaukee runs were surrendered by Paul Maholm (12-10), who was touched for nine hits in 4 1/3 innings. The three straight Atlanta losses have come after the Braves had won five in a row.