WASHINGTON • Scientists say climate change is increasing the likelihood of lightning strikes across the United States, after lightning struck at a square near the White House, leaving three people dead and another in critical condition.
The hot, humid conditions in Washington on Thursday were primed for electricity. Air temperatures topped out at 34 deg C - or 3 deg C higher than the 30-year normal maximum temperature for Aug 4, according to the National Weather Service.
More heat can draw more moisture into the atmosphere while also encouraging rapid updraughts - two key factors for charged particles, which lead to lightning.
A study released in 2014 in the journal Science warned that the number of lightning strikes could increase by 50 per cent in this century in the US, with each 1 deg C of warming translating into a 12 per cent rise in the number of lightning strikes.
Fast-warming Alaska has seen a 17 per cent rise in lightning activity since the cooler 1980s.
And in typically dry California, a siege of some 14,000 lightning strikes in August 2020 sparked some of the state's biggest wildfires on record.
Beyond the US, there is evidence that lightning strikes are also increasing in India and Brazil.
But even as the number of strikes increases, being hit by one is still extremely rare in the US, experts say.
About 40 million lightning bolts touch down in the country every year, according to the Centres for Disease Control (CDC) - with the odds of being struck less than one in a million.
Among those who are hit, about 90 per cent survive the ordeal, the CDC says. The country counted 444 deaths from lightning strikes from 2006 until last year.
The two men and two women struck by lightning on Thursday while visiting Washington's Lafayette Square, just north of the White House, were among the unlucky few - struck by a bolt that hit the ground during a violent, afternoon thunderstorm.
The lightning hit near a tree that stands metres away from the fence that surrounds the presidential residence and offices across from the square, which is often crowded with visitors, especially in the summer months.
All four victims suffered critical, life-threatening injuries, and were taken to area hospitals.
Two of them later died: Mr James Mueller, 76, and Mrs Donna Mueller, 75, from Janesville, Wisconsin, the Metropolitan Police Department said.
"We are saddened by the tragic loss of life," the White House said in a statement on Friday.
"Our hearts are with the families who lost loved ones, and we are praying for those still fighting for their lives."
Later on Friday, a third victim - a 29-year-old man - was pronounced dead, the Metropolitan Police Department said.
Further details on the victim were being withheld until the next of kin were notified.
Because heat and moisture are often needed to make lightning, most strikes happen in the summer.
In the US, the populous, subtropical state of Florida sees the most people killed by lightning.