What? Well... how about sitting still, reading a book (a kindle does not sound right) with a nice warm cup of your favorite beverage with music playing lightly in the background? Working on your craft with your pet snuggled by your side?
Too sedentary? How about something in the kitchen where the activity usually creates "down-home aromas? Like baking some yeastd bread? Oooh, the smell of yeast bread rising. Cookies, Cakes? Roasting coffee is ambrosia to me but my wife smells it differently.
By the way, mopping the kitchen floor is not the aroma or activity I was seeking, but it may to you so..... whatever works. What would be a perfect rainy day thing to do, sleep? That one slipped my brain until right now. I might think of a nap once the kids settle down. Right now they are wearing the floor and carpet out with races. (It must be a full moon behind those clouds)
It is also a good day to get some postponed maintenance done on your garden equipment. I have three gas weedeaters, a riding and push mower, a full fledged tiller and a Mantiss tiller that need that form of attention. Will they get it? I am probably going to defer to listing/maintaining ebay items, roasting the coffee and the nap, of course. A little chillier outside than I would like for activities in unheated spaces.
Maybe getting caught up on correspondence or a phone call to a friend? That's a good one to not put off as we get up in years. ;-)