When you ride your scooter, your forehead sticks out of the car, so you have to carry it. The scooter doesn't fit in the car when you aren't on it though, so you have to carry it out the window. And it takes a lot of luck not to get clipped by a car or accidentally take out a pedestrian with it.
As you carry the scooter, your luck turns, and it starts to rain, so you pull out your umbrella (うん). Now you're holding your scooter, your forehead, and an umbrella outside of the car.