I just found this concerning the Darlington weather situation. Cup race tomorrow moved to 6 PM start because of rain. Here is the potential schedule with the rain:
If today's XFINITY race cannot be run, it will be rescheduled for 12:00pm/et Thursday.
If both XFINITY and Wednesday’s Cup race are postponed, XFINITY will compete at 12:00pm/et and Cup at 7:00pm/et on Thurday.
If just Cup is postponed, it will be made up at 12:00pm/et Thursday.