This is completely normal. This is also exactly why you shouldn’t constantly weigh yourself. Weigh yourself once a week, first thing in the morning after you’ve been to the loo
I disagree and it's exactly why you should weigh yourself more often, or at least appreciate the reasons why weight varies that has nothing to do with body fat percentage which is the only thing that is of concern.
Bodies don't follow a 7 day cycle so you have no idea if that day is a heavy or a light day. If you weigh yourself more often, you would know that it is not possible to gain or lose 2 kg of fat in a day - you'd need a calorie deficit or excess of 7000 calories.
In scientific circles we call this uncertainties. The study of variations in measurements, because just because the scales say 10 stone, for example, all that is saying is that 'this person weighs somewhere between 9.5 stone and 10.5 stone'. Yes, really, if you scientifically accounted for all the uncertainties, they would be about half a stone for a 10 stone person, due to:
Variation in the scales - the number really isn't bang accurate and for analogue scales, there is the parallax error.
Consistency of flooring/standing directly in the middle etc
For women, affect of the menstrual cycle
Hydration levels
What food/drink is going through your system.
Changes in body composition - muscle/fat ratios
Weight isn't really a great thing to measure because it doesn't tell you much about how slim or healthy you are, which is what you should be concerned about. It's just the easiest thing to measure, but almost no-one appreciates that it's not really being measured very well.