Mick Schumacher was denied his Formula One debut after opening practice for the Eifel Grand Prix was abandoned due to bad weather.
But persistent drizzle and low clouds meant the medical helicopter could not fly at the Nurburgring, with the decision eventually taken to call off the running.
The second practice session, scheduled for 3pm local time, was also in doubt with bad weather forecast to continue throughout the day.
Schumacher, the 21-year-old who leads F1's feeder series Formula Two, will have to wait for his maiden grand prix outing. British driver Callum Ilott had also been due to make his first appearance, driving for Haas.
Hamilton was also bidding to match Schumacher's victory record of 91 wins on Sunday.