Unexpected rain less than 24 hours after staining
I just love how manufacturers expect that weather be so predictable that one could be assured of no rain in the next 24&ndash;48 hours.

Here, in the land of the world's most unpredictable weather, we often cross our fingers, resigned to repaint.  Or put up tarps to deal with the possibility of rain, or tarps are at the ready in case threatening clouds appear.

If the temperature and humidity were conducive to quick curing before the rain, it is probably okay.  More rain won't make much difference, especially if the rain stops and the humidity goes down in a few hours.

If there are a few patches of not-well-cured paint, try gentle use of a hair dryer.  In a few days, see if any touch up is needed.