Yeah, that's a pleasant snowfall on Google's Search page when I typed in 'Let it snow'. This is yet another Google's search query tricks after the barrel roll trick.
As soon as you hit the search button, little snowflakes will start falling down from the top and by the time you enjoy the view it will freeze up the page with snow. Start dragging over your mouse over it and it will wipe of little by little. Well, yeah Christmas is here and Google wins over hearts by such lovely tricks. Click the “defrost” button and again you’ll see a clear screen.
Enjoy! Happy Christmas.