How does water damages the phone lines?
Too long for comment:
To expand on @passerby a bit - the noise you hear is the result of the water forming a partial short-circuit between the two wires that come to your house from the telephone exchange; because of various chemical effects due to electrolysis, gassing, etc this is a lot more noisy than bridging the line with the equivalent resistor. Often the characteristics of this partial short are such that it will 'ring on' - ie application of the higher-voltage AC ringing will cause the resistance to drop; this appears to the exchange equipment as if you have answered the phone, and it will stop the ringing current and open the transmission circuit; this kind of fault is called 'Ring Trip' in (British) telephone engineering jargon.