When I brought Morgan home in February it did nothing but rain and he refused point blank to go out and wee/poo. I'd have to go out with the umbrella and treats and he'd follow and then start the constact round of "Be Clean" till he eventually went. He's a bit better now with the rain but not much!
What you are describing sounds very much like my first pup. I'd stand outside with her, it wouldn't be raining, for 30 mins and not a sign of anything and then we'd be back inside 2 mins and she'd go. Toilet training is one of theee most frustating things.........but take heart it will get better.
Even our grown up pooches have their moments too. A few weeks ago Barney, who was toilet trained by 15 weeks and is now 16 months, decided to wee in the lounge despite the door to the kitchen being open and the kitchen door to the drive being open.
It was raining, but he's not bothered by it, so what was that all about? Who knows.
Just one of those blips I guess.