In order of occurance...
Lose the umbrella you want to use. Spend half an hour pulling the house apart, and eventually settle on using your father's mighty-expensive Italian one.
Realise that while you had expected drizzle, you hadn't expected your original location to have turned into a bog. Wade your way through in wellies.
Realise your ingenious plan to shelter the camera with a waterproof hood has one flaw: you can see neither the screen nor the viewfinder when they're covered over. Thus, spend ten minutes figuring out a way to keeping the camera dry retaining the ability to see what you're shooting.
Manual focus. Need I say more?
Realise the rain is getting heavier. Also, the wind has picked up. Worry about the tripod falling over every time you walk more than three steps away.
Cold and sodden, hope that there is at least one decent shot in your stash and start to pack up. Knock everything over in your rush to get back to dry warmth, including father's said expensive umbrella. Spend more time getting the mud off it.
Use hair clips you found in your pocket to fasten your camera bag, as your fingers are too cold to use the clasp.
Sometimes I wonder why I do these things.