Howard started the game's scoring with a solo homer in the second off Braves starter Javier Vazquez, but Atlanta would answer in the bottom half of the fourth inning with a solo home run by Matt Diaz.
However, Howard would save his knockout blow for the sixth after Jimmy Rollins and Shane Victorino each singled to start the inning against Vazquez. Behind in the count 1-0 to Howard, Vazquez hung a changeup and Howard launched it 378 feet into the right-field seats to give the Phillies all the runs they would need.
"I'm just trying to see the ball," Howard said. "I got some good swings on it tonight. Fortunately for us, they wound up on the other side of the fence."
"He has always hit good in September, and maybe now he's starting in August," Manuel said of Howard's power surge. "He stayed on the ball real good. When he doesn't stay on the ball, he swings and misses. But you never know when he's going to stay on it. You can get two by him, and he'll smoke the third one out of there."
The four runs were more than enough for Phillies starter J.A. Happ, who struggled with his control early, but allowed just three hits. He hit Garret Anderson in the first and surrendered a double to Brian McCann, putting runners on second and third with two outs. Fortunately for the Phillies, Happ got out of the jam unscathed by striking out Yunel Escobar to end the threat.
Although the southpaw walked six batters, he struck out three and went 7 2/3 innings by stranding seven Braves on base. He also got into trouble in the sixth, when he loaded the bases by surrendering two walks and a single, but he got Ryan Church to fly out to again escape trouble.
"He threw well tonight and he's got that late life on his fastball that makes his fastball look very good," Diaz said of Happ. "When you cheat on his fastball, it makes his offspeed pitches look very good. He has an idea of how to pitch, and he's got a catcher back there that knows how to work it. He's having a good year."
Sunday's performance was the second impressive outing of the season for Happ against the Braves. On July 2, Happ went seven innings and allowed just two earned runs, but took the loss.
"They're a good-hitting ballclub," Happ said of the Braves. "I've seen them a few times now. More than anything, it's just trusting [Phillies catcher Carlos Ruiz] behind the plate. That's the biggest thing."
In 280 career at-bats against the Braves, Howard is hitting .332 with 27 home runs and 79 RBIs, meaning he averages a homer once about every 10 at-bats. In this weekend's series, Howard went 4-for-11 and drove in six of the 12 runs the Phillies scored.
His multihomer game was the 20th of his career and his third this season. He is now tied for third on the Phillies' all-time list for multihomer games with Dick Allen.
Brad Lidge got the final out of Sunday's finale to earn his 23rd save, one day after blowing a save and taking the loss.
Apparently, the long rain delay had little effect on Howard's concentration. The Phillies' slugger said he spent the delay relaxing and waiting to hear when he would get a chance to play.
"I think as far as a rain delay goes, most guys would rather have it before the game starts," Howard said. "If the game starts, you go out and do your routine, and then you have to cool off and try to get back out there."