I can easily be 4-5 pounds heavier at the end of the day compared to the start, which is why I'm trying to get out of the habit of weighing myself obsessively! Water retention at time of the month can add a good 4 pounds too.
It seems to vary a lot from person to person, but remember that a LOT of your weight IS water weight (over half of your weight includes water). There's water in our muscles and all throughout our bodies.
My weight varies 2 to 4 pounds sometimes. Who cares if it's water weight, food eaten, lack of regularity or a new limb I've magically grown overnight! The point is the change over time. Weighing once a week or less is the best way to see that.
Sometimes I will weigh myself before and after a workout, and the difference will be about 5-6 pounds every time, just based on the water I was drinking while running.