Traditional works as well in the rain, key is to not use fairy, that layer of soap breaks up and leaves spots. Not so with Squeegee off or GG3/4. I used to dread it though, all the microfibres wet, really annoying. Now with wfp I'm laughing my way through, don't even care.
Customers need to be trained just like when switching to wfp. I've done a lot of houses in torrential weather, and then sun came out, and they dried beautifully.