Instructables user stickmop shares a trick to tell basic barometric pressure using a hot cup of coffee, tea or cocoa: watch the bubbles when you pour the coffee into the cup.
If they move to the edge of the cup quickly, you can expect clear skies for the next 12 hours. If they hang out in the centre, expect rain in the next 12 hours. And if the bubbles move slowly to the edge, you may get a bit of weather, but it will clear soon.
This trick came from a long ago issue of Backpacker Magazine. If you're out camping without an internet connection it may come in handy someday.
Predict weather with a cup of coffee [Instructables]