It's windy today and I noticed that the water level in the toilet is lower than normal. I've also noticed on other days that the level fluctuates along with the sound of the wind outside. None of the other faucets and such seem to be affected.

 

My guess is that as the wind blows over the drains all along the street a small vacuum/sucking effect is created.

 

Anyone know the real answer or have other ideas?

There is a vent pipe from the toilet that goes up through the roof. Maybe the wind changes the pressure in the pipe which in turn changes the level of water in the toilet. I'm not sure that that makes sense - it would seem that the water in the bowl would be governed by the water sent in from the tank. Is there a plumber in the house?

I thought the toilet was just being affected by atmospheric pressure, but that might just be in my head.