The National Weather Service office in San Juan warned on Oct 29 that vulnerable areas of Puerto Rico may see coastal flooding from exceptionally high tides.^[1] The warning is aimed at communities along the coast. The office tied the risk to tides it described as exceptionally high. For a reader who lives near the water, that is the detail to hold onto: the flooding threat comes from the tides, not from rain. The notice did not name specific towns or give a window for when the highest tides would arrive. It flagged the risk for areas it called vulnerable.