It's not the first time that practice sessions or championship races have been postponed or canceled due to bad weather.
The problem was rarely caused by unpredictable events. Remember 2008 in Indianapolis. The 250 race was canceled due to hurricane Ike (but both the 125 and the MotoGP races were held under the downpour).
Then there was a postponement in Qatar in 2009 caused by torrential rain (in the desert!). The Grand Prix was postponed until the following Monday.
It was a nightmare because they had to change all the airline reservations and even reorganize the logistics, but Losail simply didn't have a water drainage system. No one expected it at that latitude.
The case was different when they cancelled the Malaysian GP in 2011. Marco Simoncelli died after the first few laps of the race. In the same year, the Japanese GP was postponed because of the volcanic ash fallout that drove airlines crazy worldwide.
The mother of all cancellations, however, remains the Austrian Grand Prix in 1980. The cause was snow: more than a meter, which had turned the Salzburg circuit into a winter resort.
They didn't even try to race. It was impossible. Everyone went home.
There is a final consideration to make. Some events are unlikely to be unpredictable, but it would be better to study the calendar avoiding months that, historically and meteorologically, can cause problems. Coming to Phillip Island in Australia at the end of October, which is the beginning of Spring, is a mistake. We're in the south here, and since we're down under, it's as if we were in the north. It should make them have some second thoughts.
The problem is the organizers, who are determined not to change the dates, but also the increased number of Grand Prixs - 20 starting in 2020 with the addition of Finland - which increasingly narrows the available spaces on the calendar.