I had a problem a couple of weeks ago, where I lost my ADSL connection for several days after a severe storm on Saturday 10th September. The router was unable to connect to the ISP. I switched it off and returned to it on Sunday to the same no connection problem. By Monday I was getting fed up and because I am unable to connect to PlusNet at work, my only remaining choice was to resurrect my modem based connection using a Virgin account.
This was when my suspicions were raised as the modem kept dropping the connection. I checked the phone several times and the dialling tone seemed fine, but just for an experiment, I rang my mobile phone to check that I could still call out. This worked fine, so I returned to the PC and found that the modem connection was now working reliably. I then retried the ADSL and got an immediate connection and it has been fine ever since.
I have noticed that after heavy rain, my BT line has a distinct crackling sound in the background.