The storm knocked out power to around 100,000 people in Houston and southeast Texas while work at oil refineries in the area was slowed or halted.
Officials in Harris County, which includes Houston, said there had been a combination of at least 1,000 high-water rescues and evacuations to get people to shelter, in anticipation of the threat lingering.
Humberto causes outage for nearly 16,000 homes, according to electricity company Belco, as the storm's eye moved closer to Atlantic archipelago.
The floods have so far claimed six lives in Spain, with train and air services were disrupted.
Early Friday, tropical disturbances swept over the central Bahamas, packing winds of 45km/h and expected to drop 8 to 13cm of rain through Sunday.
The victims, aged 51 and 61, were killed in the region of Castilla La Mancha after torrential rain dragged their car and flipped it over.
NBC, citing a representative for Prime Minister Hubert Minnis, said the official count is now 43 and the number is expected to rise significantly.
At least seven deaths were reported in the Bahamas. The storm's punishing winds and muddy brown floodwaters severely damaged thousands of homes, crippled hospitals and trapped people in attics.
Hurricane Dorian came to a catastrophic daylong halt over the northwest Bahamas, flooding the islands of Abaco and Grand Bahama with walls of water that lapped into the second storeys of buildings. The storm spurred evacuations in southeastern US.
Hurricane Dorian battered the islands of Great Abaco and Grand Bahama, killing at least five people, peeling off roofs, toppling cars and snapping power lines as rising floodwater threatened to engulf houses.
Hurricane Dorian slammed into the northern Bahamas as a monster Category 5 storm on Sunday.
Hurricane Dorian is expected to become a potentially catastrophic Category 4 and to approach the northwestern Bahamas on Saturday
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