Rear suspension noise only in rain

Hi guys

Have a bit of a weird problem. I get a clunking noise on the rear of my e36 only when it rains. When it's dry there's no noise. The noise is pronounced when going over bumps and most so when going over speed bumps. Noise seems to be coming from the LHS but doesn't seem to affect ride or handling.

Any input/guidance would be appreciated.

Thanks for reading

Neven