Of course I was kidding. But you'd be surprised how much urine is released by young strapping males. At least a pint each. However, you are also forgetting one other important fact. There is always ambient moisture in the wetter areas of the world and Europe is one of these. Moisture only has to reach a cascade point to become rain. A few thousand pints of urine and considerable amount of sweat might be just enough to trigger a cascade moment in the atmospheric moisture level. Moreover, the air does not have to be perfectly still (and seldom is) and humidity is the ambient moisture level (or did you not know this?) It is a given that temperature is important, at least for the speed of evaporation and struggling, battling bodies produced a tremendous amount of both heat and sweat (at least a quart an hour) not to mention blood and other moist body ejecta. Moreover, temperature becomes naturally cooler the higher you go in elevation and may even turn into snow (or did you not know this either?) And it doesn't have to be a heavy rain, although I suspect, when it does rain in Europe it is seldom light (depending on the topography). Also there is a very big difference between "rain" and a "storm." I don't believe the OP mentions a "storm" after every battle only that it apparently rains.
haette erstmal googeln sollen(in verschiedenen Sprachen) anstatt mich von euch laecherlich machen zu lassen.