Weather Seeds show the exact times for shooting stars, as well as rain, and other weather conditions. We use it mostly for shooting stars, likewise if we know there will be shooting stars we can look for Celeste to get star related diys. Celeste is not there every time there are shooting stars. Knowing when it will be raining helps with getting bugs and the rain fish.
At one time we only used time travel for short periods, now we leave the Switch stay there for weeks at a time. We keep the same day of the week, and time of day, just a different starting date.
We restarted my island last Tuesday (game date Dec 31, 2024), last evening we got the weather seed it looks like this: