medical services organization is all powered by generators. >> reporter: puerto rico could see up to six inches and more mountainous areas could see up to ten. heavy rain already affecting parts of the british and u.s. virgin islands which forecasters say could see up to four to ten inches in just a couple of hours time. one resident capturing on camera a bright blue surge of electricity hitting a transformer in the midst of all of the rain. >> this is not a good place to be. in the next two or three days. the good news is, is this will be a very quick storm. this will come through in six or search hours and be over and we can assess the damage. >> reporter: tonight, puerto ricans are not taking any chances, many homes and businesses already boarded up, boats removed from the water, drivers are all filling up their tanks. shelters are open on the island ahead of what could be a busy weekend. meanwhile, in florida, major preparations are also under way, with the storm expected to make landfall there during the labor day weekend. >> we've done this before.