I tried to do some research on air density as I was aware of pellets dropping faster over water and although I couldn't do any useful maths, I did find out that air density in the UK can vary by about 10% and 10% of anything is big enough to change the fragile trajectory of an air gun pellet.
Higher humidity must also cause more resistance to a pellets flight, but I'm in no hurry to fit a hygrometer to my gun! As most people re-zero their gun before a shoot this will eliminate most of these variables anyway.
However, when you get to a lane incorperating water you will get denser air and probably higher humidity and so briefly you will have that extra drop to deal with.
Anschutz 2013 MEC1 .22LR
Miroku 3800 12bore