Are parameters like temperature, humidity, wind, rain and snowfall important for boats and ships (large and small ones) that travel on rivers? In which way are the ships or the crew affected, and to what extent is the weather important?

Meteorology is my hobby and maritime training is my profession so I feel I should be able to answer your question but … gosh, I can’t think of any meteorological factor that would affect vessel traffic on rivers. Even fog would have little importance on a river. I have sailed myself a lot and I am used to make decisions on the weather but once on a river or a canal, there is nothing I would worry about on departure than maybe the time of the tide, if the river is tidal. For example, sailing into Hamburg on the river Elbe, due to the river output, the tide runs 5 hours in and 7 hours out. The tidal stream reaches maybe 4 knots at spring tides and is enough to be considered in the navigation. But the weather … no, it won’t disturb any vessel I can think of.