Our girls also hate going potty in the rain. My solution was to put down a pee pad in the garage, which they happily use and stay dry and warm at the same time!!! It also means Mommy does not have to stand shivering in the winter rain, waiting for her little darlin's to go pee etc. I have used this method for years, and even had a doggie door installed from our house to the garage. In summer it is "boarded up", so they know to go outside.
If you live in an apartment building, if there is a basement garage, this method could still work, especially if it is really cold outside. Just make sure you clean up the poops...
