Sunday’s Emilia Romagna Grand Prix has been called off after a rising death toll caused by major flooding in northern Italy.
Earliest reports say at least three people have died amid widespread destruction and landslides. Some communities have been warned to move to higher ground.
The Imola race was scheduled to be the sixth round and the first swing through Europe of the global nine-month championship.
It was part of a triple-header on successive weekends in Italy, Monaco and Spain.
But after discussions between local authorities and race organisers F1 bosses announced Wednesday the decision was taken because “it is not possible to safely hold the event for our fans and it was the right and responsible thing to do”
The move came after Italian deputy prime minister Matteo Salvini called for the race to be postponed to help emergency services.
Fierce rains have made many roads impassable and some cars left entirely submerged.
Although forecasters have predicted the downpour would ease on Thursday it is expected to return with fresh venom on Friday and Saturday when the F1 practice and qualifying schedules would be in full flow.
The race would have expected to attract more than 100,000 fans over three days.
In a joint statement the FIA President, local mayor and regional president said: “It would not be right to put further pressure on the local authorities and emergency services at this difficult time.”
F1 CEO Stefano Domenicali said: “It is such a tragedy to see what has happened to Imola and Emilia Romagna, the town and region that I grew up in, and my thoughts and prayers are with the victims of the flooding and the families and communities affected.
“The decision that has been taken is the right one for everyone in the local communities and the F1 family as we need to ensure safety and not create extra burden for the authorities while they deal with this very awful situation.
The decision comes after a red weather warning was issued for the region on Tuesday and Wednesday.
Two leading F1 teams are based in the Emilia Romagna region, Ferrari and AlphaTauri.
Faenza-based AlphaTauri, sister team to champions Red Bull, publicly admitted to being “very concerned about events unfolding” and the considerable damage.
They added: “The team's factory is currently unaffected and everything is being done to ensure the safety of our employees and their families.”
Ferrari headquarters are at Maranello 100 kilometres north-west of the circuit.
Track workers constructing motorhomes in the F1 paddock were evacuated on Tuesday.
Parts of the Imola track runs within feet of the Santerno river with real concerns it could burst its banks.
F1 staff, team members and journalists were forbidden from entering the circuit on Wednesday after heavy overnight rain.
Organisers said they will discuss rescheduling Imola but it is considered unlikely given the packed 22-race schedule and intense travelling required.
Cancellation of the race is a double setback for title rivals Ferrari and Mercedes who were both planning to debut dramatic upgrades in a bid to get back on level terms with runaway championship leaders Red Bull, winners of all of the first five rounds.
Ferrari sources say they will now delay the unveiling of a new rear suspension package until the Spanish GP in Barcelona on June 4.
Mercedes, more woefully adrift than they have been in nearly a decade, are banking on one of the biggest in-season overhauls in their history with new bodywork, aerodynamic floor beneath the car and new front suspension.
Even Lewis Hamilton, his future in limbo, has admitted he is counting the hours until the improvements appear.
It is remarkable to reflect rumours of a redesign first surfaced at Imola last year and in a sport measured to a thousandth of a second Mercedes are only really grasping the nettle now, 12 months down the line.