In this report, Role of Ions in Body Chemistry there is an analogous connection between rainfall and taking a shower.
“..a shower will re-ionise and has a tonic effect on the body, just like rainwater which clears the air.”
I think most people can attest to feeling better after showering or standing under a waterfall or walking in the rain; the thrill of getting splattered on is enough but now you really know why. Moving water creates negative (positive for us) ions. Good thing I splash around in the tub and take an occasional shower.
Next time: Hot Springs, Onsen, and The Cold Plunge.