Soriano hit a solo homer in the fourth inning and a three-run shot in the fifth off Ian Kennedy and added a run-scoring double in the seventh off Brad Ziegler.
Even though it wasn't raining at the time, the Cubs held up the start of the game after radar showed a big storm coming toward Wrigley Field. When it finally arrived, the deluge soaked the warning tracks and bullpens on either side of the field, creating ankle-deep water in some spots. The game didn't start for 3 hours and 40 minutes after the scheduled first pitch.
Soriano launched his 16th homer leading off the fourth, a shot to left that cleared the bleachers and put the Cubs up 2-1. And with two outs and two on the fifth, he hit a high drive that landed over the fence in center to make it 5-1.
It was Soriano's s second multi-homer game this season and 30th of his career. The 36-year-old slugger has hit all of his 17 homers this season since May 15. His five RBIs tied a career high.
Kennedy (6-8) gave up seven hits and six runs in five-plus innings, hitting a batter, walking two and throwing two wild pitches.
Paul Maholm (7-6) allowed six hits and a run in seven innings to win his third straight start. He drove in a run with a bunt in the sixth inning.
After four days off for the All-Star break and then the long delay, the Diamondbacks came out ready to go as Willie Bloomquist led off with a double and Aaron Hill beat out a bunt single. Bloomquist scored on Justin Upton's double play grounder, the first of two double plays turned by the Cubs in the first two innings.
Kennedy's wildness helped Chicago tie it in the second. Soriano led off with a double, reached third on a fly and scored on Kennedy's wild pitch.
Maholm had his shortest start of the season when he faced the Diamondbacks on June 23 in Phoenix, lasting 3 1-2 innings and giving up nine hits and six earned runs. He hasn't lost since that outing.
NOTES: The Cubs have won 10 of their last 14. ... Diamondbacks RHP Daniel Hudson had successful Tommy John surgery on Monday in Los Angeles. It was performed by Dr. Lewis Yocum. ... Cubs 3B Ian Stewart had surgery on his left wrist Tuesday in Cleveland. The team will determine in August if he will play again this season. .., Arizona RHP Josh Collmenter will move back to bullpen with LHP Joe Saunders (left shoulder strain) returning to start Saturday after coming off the DL. ... Announced attendance was 36,878.