How often does fuel dumping from planes in flight actually occur? There are a couple of questions about the emergency procedure of fuel dumping, used to reduce the weight of airplanes to be able to land.

This is certainly interesting, regarding environmental affects, safety aspects, and maybe some archaic fascination for huge fuel-air clouds.

How relevant these questions really are depends on how often fuel dumping is done.

But I don't know how often it is actually done, in incidents per year globally.

I understand that the procedure is used only in emergency cases, but not only in very few very extreme situations. It's about getting the weight down to be able to land safely, and the overweight is from fuel not yet used up on the flight.

So the procedure is needed whenever there is a need to urgently land, and there is not enough time to burn the fuel in flight.

That seems to mean that severe medical emergencies of individual passengers may be a reason? That happens much more often than drastic technical problems I assume, so it would be a strong factor.

Now, I'm interested in some rough total estimate about how often fuel dumping happens, and the main factors, like minimal emergency cases that can lead to a fuel dump.

I'd simplify the scope by considering only commercial aviation, ignoring military and general aviation - but I do not see that as important, use the data you have at hand.
These two reports cite that the US Air Force at one time jettisoned fuel nearly 1000 times per year. The second report also mentions that commercial airlines reported 485 instances of fuel jettison over a 5 year period. The commercial reports are only for maintenance related cases though, not including scheduling or weather reasons.

Both of these figures date from the 1970s. Military standards have been changed since then to reduce the frequency of it. The first paper assumed that in 1995, military fuel jettisoning was "infrequent".