It all depends on the person and how his/her body manages the weight loss. For example, sometimes the body will resist loss by filling the empty fat cells with water so that the scale doesn't move down at all even though fat has been lost. Eventually, that water will be dropped, but we can't control that.
I've lost a great deal of weight recently but because I'm post-menopausal and hypothyroid, it was very slow--averaging one pound a week. Then suddenly, I showed no loss at all for 3 weeks, and then I went down 4 lbs in the 4th week. The same loss for the month as I'd been having, but I have no idea why that loss showed all at once. It happened again the following month, and then I returned to my single pound loss each week.
What has helped me learn about my body is I weigh only once a week, and I mark that weight on a calendar. This enables me to see the 'patterns' in my loss over time.
Don't focus on the scale or 'when' the loss happens. I find it's much more productive to focus on eating according to my plan, and checking on what the effect is on a weekly basis.