You can weigh any time as you'd like, just be consistent with when you weigh. Many members prefer to weigh themselves first thing in the morning after they go to the bathroom. Some weigh with clothes. Some weigh nekkid.
Also, if you tie your emotions to the scale, don't weigh yourself every day. Once a week is fine. You really won't see a dramatic change in the scale from day to day. If you do, it's a water weight fluctuation, not a fat loss.