According to the National Weather Service: The combination of dangerous storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline. Surge-related flooding depends on the tidal cycle.
According to the National Hurricane Center, the slow movement of Beta could cause a prolonged period of rain. It could be especially dangerous from High Tide on Sunday (9-20-2020) through Tuesday. Tropical storm force winds are expected to begin Sunday night.
graphic: National Weather Service