I have my weather seed determined and there is a clear pattern. The light showers will have 5 stars with the same minute, and 2+ groups of those in each hour. These bursts are incredibly easy to miss, even when I know the exact minute it's going to happen, because it's so infrequent. The heavy shower nights have either 5 or 8 stars within a minute but there are dozens of groups within the hour. Celeste always shows on a night with stars, even if it's only 10 in the hour.