Energy network corporation Ercot says 104,000 customers are already without power. Electricity company AEP Texas says it has 2,000 personnel ready to start restoring power once it is safe to do so. Ercot has urged people to stay away from downed power lines.
The National Weather Service makes the point that the last category 4 storm to hit Texas was Hurricane Carla in 1961. It killed 34 people, destroyed thousands of buildings and led to a repair bill of at least $300m.
Donald Trump has signed a disaster proclamation. This quickly unlocks federal funds and resources to deal with the disaster and was done at the request of Greg Abbott, the Republican governor of Texas.
Abbott on Wednesday preemptively declared a state of disaster for 30 counties to speed up deployment of state resources.
90% of the town of Port Aransas has evacuated ahead of the storm but officials have no idea how many people are still in the city of Corpus Christi just south of where Harvey has hit. The city has a population of 325,000.
Our correspondent Tom Dart is in Houston right now, where the storm is making its presence felt 200 miles away. The storm is expected to head towards the city’s metropolitan area, which is home to 6.8 million people.
Houston receives about 50 inches of rain on average a year. Harris County, which includes Houston, is one of 14 counties under a tornado watch until 2am local time on Saturday, with fears that the arriving storm could spawn ideal conditions for tornado development.
One of the key concerns is flooding because the storm is predicted to now move up the coast towards Houston and stall for days, bringing continual rainfall. Forecasters have warned of rising sea levels and 25 inches (63cm) or more of rain in some areas. Here is how things are going in Port Aransas, about 20 miles from Rockport.
Patrick Rios, the mayor of the town of Rockport, where the storm has hit, has urged residents who chose to stay to write their social security numbers on their arms to make it easier for rescuers to identify them.
He told KIII-TV of Corpus Christi earlier that Harvey “is a life-threatening storm” and that those who stay “should make some type of preparation to mark their arm with a Sharpie pen”.
Local officials along the Texas coast urged residents to take precautions and, if they were in the direct path of the storm, to evacuate. Thousands of people have headed north so far.
An observation post in Port Aransas very close to where the hurricane has made landfall is reporting sustained winds of 102mph (164km/h) and gusts of up to 120mph (193km/h).
Fuelled by warm Gulf of Mexico waters, Harvey grew from a category 1 early in the morning to a category 4 by evening. It went from an unnamed storm to in just 56 hours, an incredibly fast intensification.
Hurricane Harvey has now hit Texas as a category 4 storm. Tens of thousands of people have evacuated an area of coast that includes oil refineries, chemical plants and the flood-prone city of Houston.
The governor of Texas, Greg Abbott, warned that the monster system would be “a very major disaster” and some have compared it to Hurricane Katrina, one of the deadliest ever to strike the US.
Dennis Feltgen, a meteorologist for the National Hurricane Center, said: “We know that we’ve got millions of people who are going to feel the impact of this storm.”
We will endeavour to keep you posted on all the latest developments here. If you see something pertinent, feel free to email me at graham.russell@theguardian.com or find me on Twitter @G_J_Russell
Jeff Lindner (@JeffLindner1)
NWS Birmingham (@NWSBirmingham)
