If you think you are having rain issues with your telephone connection, get your garden hose and SOAK the area where your phone wires are buried the morning that the repairman is coming out to service your home. SOAK the side of the house where the rain hits it. SOAK anywhere that you think there might be a telephone wire or connection box. If you have wires stapled to the outside of your house, SOAK them too.
The phone man is NOT going to use your water to soak telephone lines because then you will have a claim against the company for part of your water bill.
Advice from a retired telephone repairman.
Thanks :) In my case it likely wouldn’t have helped as the problem was eventually found in a switching box up the street that wasn’t sealed properly.