If you wait until you put your suit on, you could be 5 pounds heavier.
After your bowl of oatmeal and coffee, add another pound and half.
Head to the gym at lunch and get on after an hour on the treadmill, you'll be down 2 pounds from water weight.
Spend the afternoon rehydrating, and you've put the pounds back on with the fluids you've replaced.
Remember, a cup of water weighs 10 ounces, so drinking 8 cups of liquid water adds temporary weight, not fat.
Think about that when you get on the scale after you've had a bean salad, soup, fiberful potato and even more water at dinner. You could be up 5 pounds from the morning, even though your body has not really put on any fat weight at all.
Another factor is where you put your scale. A thick carpet or texture tile can decrease your number by 20 pounds or more. Try putting a barbell on your scale to test the accuracy.
Weigh in the same spot at the same time to keep most other factors from coming into play.
If you've been hitting the gym hard, it's also possible you will drop body fat while increasing weight. But realize that it takes about a month of pretty serious strength training to add one single pound of muscle.
If you're up a few but ate well the day before, your hormones might be messing with you, so keep up the good work.
If you consider that a pound of fat requires 3,500 extra calories consumed and you're up two pounds, you've got to ask yourself if you really consumed an extra 7,000 calories to have earned those 2 pounds. Most likely, you haven't.