My very wise and wonderful sister tells me
a pint of water weighs a pound and a quarter.......
so, if you had anything to drink then along with wet hair and water infused skin after said shower, you will weigh more!
Stick with the first weigh in of the morning and don't weigh twice in one day (unless, as Cybill said, she has done it out of curiosity to see how her body fluctuates during the day).