The decision to bring forward the start time to 13:00 local time (18:00 BST) was made on the eve of the race by the sport's governing body FIA, along with commercial rights holders and local promoters.
Organizers acted "due to the weather forecast that is expected to bring heavier rainstorms later in the afternoon close to the original planned race start time," they said in a statement.
"This decision has been taken to ensure the least amount of disruption to the race, and to ensure the maximum possible window to complete the Grand Prix in the best conditions and to prioritise the safety of drivers, fans, teams and staff."
Mercedes' championship-leading teenager Kimi Antonelli will start in pole position, after he resisted a late charge by Red Bull's four-time champion Max Verstappen in Saturday's qualifying session.
Charles Leclerc was third quickest in his Ferrari while world champion Lando Norris, who won the weekend's sprint race, will start his McLaren from fourth in Sunday's grid.