It settles on the results
Not just the floor. Every block on the page grows a white lip along its top edge, thicker the longer you leave it, and the search field ends up wearing a little cap. The drifts along the bottom build unevenly depending on where the wind pushed the flakes.
Wipe the glass
Wait about ten seconds first, otherwise there is nothing to wipe. Once it has properly frosted, hold the mouse down and drag. You get a smeared arc, not a clean window, and it refreezes slowly at the edges while snow keeps landing in the gap you made.
It was a December thing
The trick ran over live results one winter and got switched off with the rest of the seasonal features. That has not slowed the searching down. Google snow, google snowfall, snow google trick, let it snow google easter egg, and every scrambled version of the phrase people half remember, still turn up every year around the same fortnight.
There is no matching rain version, though people go looking for one. For weather with a fan behind it, google fan moves air across the same kind of layout, and google underwater puts the whole thing in water.
Does the frost affect the page?
No. It is a layer over the top. Clearing it changes what you can see and nothing else.