Josef Newgarden rocketed to his third victory at Barber Motorsports Park in the last four years after dominating Monday's delayed Verizon IndyCar Series Grand Prix of Alabama.

Heavy rain on Sunday had caused the race to be red flagged after 23 laps, with the remaining 67 laps postponed until Monday.

Newgarden led the field away for the green flag in dryer conditions and was able to quickly forge a lead, going unchallenged through the one and only cycle of dry pit stops on Lap 49.

The Penske driver's stop allowed Sebastien Bourdais to move into the lead for six laps after Dale Coyne Racing opted to roll the dice on strategy, only for another band of rain to arrive and leave teams pondering a switch to wet tyres for the closing stages.

Penske was the first to make the switch with Newgarden, bringing him in at the end of Lap 71, while Coyne kept Bourdais out on dry tyres in the hope that the shower would pass and allow him to snatch away victory.

Conditions became too poor for Bourdais to stay out, forcing him to pit and give the lead back to Newgarden on Lap 76, who was able to complete the final six laps before hitting the two-hour time limit with a lead of 9.9 seconds at the chequered flag.

Ryan Hunter-Reay took second place for Andretti Autosport ahead of Schmidt Peterson Motorsports teammates James Hinchcliffe and Robert Wickens, with Bourdais ultimately settling for fifth after his strategy gamble.

Scott Dixon led Chip Ganassi Racing's charge in P6 ahead of Graham Rahal and Takuma Sato. Simon Pagenaud took ninth, albeit in frustrated fashion following a run-in with Gabby Chaves. Marco Andretti completed the top 10 ahead of Alexander Rossi, who lost the lead at the top of the drivers' championship after Newgarden's victory, who is now 13 points clear for Penske.

IndyCar returns in three weeks' time with the Grand Prix of Indianapolis on the Indianapolis Motor Speedway road course, kicking off the 'Monthy of May' festivities at the circuit.