I’ve had it explained to me that it evaporates in the heat and gets deposited in the mountains and the atmosphere above the more northern states, where .. once things cool down, it condenses and moves through tributaries in a big rush or two during the massive temperature changes of October/November.

The thunder storms we’ve had in Vienna in the last few years have produced amazing floods - reminiscent of the desert storms of Australias north-west, where I am from - and a couple years back, the engineering of Viennas water ways was put to the test, with the floods overflowing railway lines and traffic arteries of the city in ways not seen much before this decade...

Finland has escaped most of the heat of Central Europe. We have had hard rains occasionally, but overall not that much more rain. From stats look like 100-150% of historic numbers.

So it has really not rained outside the high pressure zone. So I am not really sure where it all would be.