You learn some funny things by taking a plumbing class at BYU. Did you know that you can estimate the wind speed outside by looking at your toilet? It's true. This is how:
This is what your toilet bowl looks like with no wind outside:
And this is what it looks like when it's really windy outside:
Did you notice the lower water level? When it's really windy outside the water level is lower in your toilet. This is because of Bernoulli's Principle. Fast wind speed lowers the outside pressure, thereby sucking the water out of the bowl. You can visualize it this way:
Pretty neat, huh? You could calibrate it if you found the actual wind speed during a windy day, then mark that point on your toilet. The you could fill in the blanks by dividing out the remaining spots.
...Well, that's assuming that the relationship between wind speed and water level is linear, which is probably isn't given the fact that the toilet is curved. So you would have to know how the bowl curved to actually do it. But still, it's a neat concept.