Bands of deadly, extreme weather including torrential rain and high winds sparked flash flooding and tornado warnings in several north eastern US states Tuesday night and into Wednesday, knocking out power for hundreds of thousands of people and playing havoc with travel.

A 32-year-old man was killed on Tuesday afternoon in a lightning strike in Monroe township, New Jersey, authorities said.

More than 11 million people from New York north to the wider New England region remained under threat of serious flash flooding on Wednesday after downpours prompted dozens of high-water rescues from vehicles and buildings.

In Paterson, New Jersey, the fire department rescued at least 20 people on Tuesday, including an elderly woman in a wheelchair. Crews plucked a family with a young child to safety from a car in Reading, Pennsylvania.

Cars were also reported trapped by floodwater in upstate New York on Wednesday morning, with authorities issuing flash flood warnings for Albany, Saratoga, Rensselaer, and Schenectady counties.

Across the north-east region, tens of thousands of people were still without power on Wednesday, according to poweroutage.us, and airports reported the cancellation of hundreds of flights.

Up to eight inches of rain was forecast for western Connecticut and western and central Massachusetts on Wednesday and Thursday, with up to 12 inches elsewhere, according to AccuWeather.

“While not all of that rain will fall at once, torrential rainfall can persist for several hours in some communities, leading to street flooding and rapid rises on small streams and drainage canals,” the outlet’s senior meteorologist Alex Sosnowski said.

The service called it “an unusually strong storm for late July” that it said would intensify across the north-east in the coming two days, triggering potentially life-threatening flash flooding.

Meanwhile, the National Weather Service (NWS) said that the intense summer “heat dome” affecting tens of millions of people across the country since before the weekend was continuing, with extreme heat warnings issued in multiple states.

“Dangerous heat continues across the southern US… bringing above normal temperatures through the remainder of the week,” the NWS said in a bulletin on Wednesday that warned of a heat index up to 115F in Texas and Oklahoma.

A combination of high temperatures and high humidity, it said, would lead to “widespread major to extreme heat risk levels, which will be hazardous to those without adequate cooling or hydration”. The heat, it said, will spread south west by Thursday.

Across the desert south-west, including Las Vegas, Phoenix and Palm Springs, AccuWeather said, temperatures could reach 120F and challenge daily record highs in some locations. High temperatures are expected to reach the mid-to upper 90s in much of southern California, including Los Angeles.

The heat, abundant sunshine, and gusty winds, the outlet said, will create a significant wildfire risk for a region stretching from California to Oregon.

On Tuesday, the NWS upgraded its assessment of a tornado that struck Wisconsin a day earlier, injuring dozens, to a category EF3 with peak winds of 145mph. The tornado traveled just over 12 miles, authorities said, ripping roofs from businesses in Menasha and destroying a house.

Officials said 68 people were treated for injuries, but none was severe.