Water weight? WTF!

I'm currently taking suggestions for solid practices on weigh-ins. Does everyone elses weight fluctuate like crazy? I weighed in this morning 4.5lbs HEAVIER than I did yesterday! I quickly checked behind me for any sneaky b-tches stepping on the scale but no one was there. I'm quite sure I wasn't involved in any competitive eating contests on the prior day so I'm a little perplexed.

I'm thinking about weighing in twice a day and taking the average?