The death toll arising from vicious storms that lashed the eastern US climbed to double digits Saturday as millions of people were left without power in sweltering conditions.

With temperatures expected to reach triple figures in Washington DC and surrounding areas on Saturday, about 3.4 million people remained without electricity – and access to air-conditioning – after power lines were wiped out by strong winds and falling branches.

States of emergency were declared in Ohio, Virginia and West Virginia, as forecasters predicted more thunderstorms and continued heat throughout Saturday.

So far, weather conditions have been blamed for at least 13 deaths – six in Virginia, two in New Jersey, two in Maryland, one in Ohio, one in Kentucky and one in Washington. In parts of Washington, residents needing assistance were urged to phone non-emergency numbers or travel directly to fire or police stations after 911 response centres were left without electricity.

Authorities also urged some homeowners to start conserving water amid concern over the effect of outages on sewage stations.

Blackouts were reported from Indiana to New Jersey on Saturday, with the bulk of the service interruptions concentrated on the capital.

On Friday, temperatures in DC reached 104F (40°C) – topping a record of 101 set in 1934. Although marginally cooler on Saturday, many were still left sweating as the mercury ticked up into triple digits.

More than 20 elderly residents at an apartment home in Indianapolis were evacuated when the facility lost power due to a downed tree.

Most were taken to a Red Cross facility to spend the night, while others who depend on oxygen assistance were given other accommodation, the fire department said.

Winds of up to 70mph also led to travel chaos as the storm battered an area spanning a number of states. On Interstate 75, near Findlay, Ohio, three tractor trailers overturned leading to lengthy tailbacks.

The deaths so far reported in relation to the storm were all thought to be the result of falling trees.

Amongst those killed was a 90-year-old woman who died when a tree slammed into her home as she slept.

Others had a lucky escape amid flying debris and swinging electricity cables.

A park police officer was injured by an uprooted tree in the northern Virginia county, and an 18-year-old man was struck by a power line. He was in stable condition after receiving CPR, authorities said.

West Virginia governor Earl Ray Tomblin declared a state of emergency after more than 500,000 customers in 27 counties were left without electricity.

At least four utility poles fell on a road in Columbus, Ohio, making it too dangerous for people in four cars to get out, police said. One person was taken to a hospital.

Early Saturday, Pepco was reporting 406,000 outages in the District of Columbia and Montgomery and Prince George's counties, Maryland.

"We have more than half our system down," said Pepco spokeswoman Myra Oppel. "This is definitely going to be a multi-day outage."

For many, the main concern was how to keep cool without home air-conditioners

Those who could afford it flocked to hotels to escape their hot, powerless homes. Others planned to spend the day at places like shopping malls in an effort to get out of the midday sun.

Jose Amaya, 41, of Germantown, Maryland, was one of millions without power on Saturday.

He said his wife and two daughters planned to go the mall to stay cool, and joked that the outage was going to cost him because they would be shopping. His wife, who works for a hotel chain, also planned to get the family a room to stay.

Robert Clements, 28, said he showered by flashlight on Friday night after power went out at his home in Fairfax, Virginia. Officers at the apartment complex where he lives said power wouldn't be back on for at least two days.

Clements' fiance, 27-year-old Ann Marie Tropiano, said she tried to go to the pool, but it was closed because there was no electricity so the pumps weren't working. She figured the electricity would eventually come back on, but she awoke to find her thermostat reading 81F (27°C) and slowly climbing. Closing the blinds and curtains didn't help.

"It feels like an oven," she said. "It is hot."

©Guardian News and Media 2012

Watch CNN video on the storms aired June 30 below:

Thunderstorm image via Shutterstock