Dog scared of rain, won't pee?

shes 5 months old and is in the process of housebreaking its raining really heavily today so i went outside with her in the rain with an umbrella but she was still really scared and hid between my legs while trembling. Then, I let her out by herself and sat on the other side of the door and i was going to let her in after she peed. instead she got even more scared and cried..she hasnt gone to the bathroom in over 12 hours and the rain won't stop..wat do i do?