A cup of coffee can predict the weather. If the bubbles form in the middle, it will be sunny and fair weather. If the bubbles form around the outside of the cup, the weather will be changing and rain or snow is on the way.
The truth to this is that in high pressure, the surface of the coffee concaves, forcing bubbles to the center thereby signaling fair weather and sunshine. In low pressure, the surface convexes thereby forcing the bubbles to the outside of the cup and the possibility of changing weather with rain and snow.