Why does our internet go out anytime it rains?

First thing I would check is that the demarc(where the coaxial line coming from street is connected to your electrical ground) has a weather enclosure box on it. If there are any splitters in there, make sure they aren't waterlogged. Next, I would suggest having a technician investigate your tap, which is your connection at the street. 

As for it being the whole node, are you aware of others in your area having the same problem?