( CNN ) -- Their stay in Parvin State Park in southwestern New Jersey was supposed to be a getaway , a chance to enjoy the wilderness and quality time with family . But when the line of strong storms came through shortly after midnight Saturday , two related families from nearby Millville decided to huddle together in a single tent hoping to ride out the strong winds and lightning together . Then , after a particularly violent gust , a pine tree snapped -- and fell right on top of them . Lives in danger as many seek refuge from extreme heat . By the time help made it to the scene , past downed trees and power lines , a 2-year-old boy was already dead , said Larry Ragonese , a spokesman for the New Jersey Department of Environmental Protection . His 7-year-old cousin later died on the way to a hospital , the spokesman added . `` The rest of the family members miraculously were virtually unscathed -- a couple of scratches , but nothing to them , '' Ragonese told CNN . `` What they have is the horror of what happened to the two boys . '' The families were n't the only ones to experience tragedy when an extreme heat spell helped spawn a powerful line of thunderstorms that swept east from Indiana to New Jersey . Millions were without power Saturday as a result , at a dangerous time given temperatures that soared past 100 degrees Fahrenheit in many of the hardest-hit locales . The combination of no electricity and extreme heat contributed to a host of unique challenges , leading officials to urge residents to do whatever they can to keep cool . Scores of cooling stations were opened up and down the East Coast . At one , in Atlanta , workers unloaded bottles of water while a resident offered advice for the city 's senior citizens . `` A lot of them do n't realize that they are suffering from dehydration . And so to come to a place that is cool , come to a place where there 's water provided , come to a place where they do n't have to worry for about 7-8 hours in 106 degree temperature , it 's really wonderful , '' said Savannah Potter . Including the two boys from South Jersey , a total of 13 people died as a result of downed trees and power lines , officials said . The millions lucky enough to survive the storms are hardly out of trouble , though , especially given the widespread power outages . 5 tips to survive extreme heat . The strong winds , heavy rains and continued heat made it feel tropical , and certainly dangerous , in inland states like Ohio . `` It looked like a hurricane you would see on television -- the rain was falling horizontally , the patio furniture was moving , '' said CNN iReporter Louis Zur Muhlen from suburbs just north of Columbus , where he spotted burning power lines in the road . `` We have pretty severe weather with thunderstorms and such , but I have never seen winds like that , and I have n't seen this kind of damage . '' Hospitals in Prince George 's County in Maryland were buzzing Saturday as people came into emergency department waiting rooms trying to get cool , said Fran Phillips , deputy secretary for the state 's Department of Health and Mental Hygiene . Water was running out in Lowell , in southeastern West Virginia , because , without electricity , the town 's water tanks could n't be refilled , water and sewer operator Matt McLeish told CNN affiliate WTAP . Residents in the town use about 50,000 gallons of water a day -- yet the main storage tank only has about 80,000 gallons left in it -- prompting officials there to urge people to conserve water . In Rockville , Maryland , a mother and daughter were dealing with more ordinary , but still disappointing concerns . They were forced to cancel the young girl 's birthday party Saturday at an ice skating rink after it lost power . The family does n't have electricity at its home . `` We 're going to the mall . Montgomery Mall we hear has air conditioning so that 's where we 're off too now , '' said mom Alicia Lucero . Photos : Extreme heat strikes East and Midwest . Will 2012 be the hottest summer on record ? CNN 's Nick Valencia , Jareen Imam , Athena Jones , Dana Ford , Maggie Schneider and Darrell Calhoun contributed to this report .
NEW : An Ohio man says he has never seen such winds and damage . Two boys , ages 7 and 2 , are killed while camping at a park in New Jersey . They 're among 13 killed in storms that left millions without power . Cooling stations open up and down the East Coast due to extreme heat .