The injured – two adult males and two adult females – were transported to area hospitals with life-threatening injuries, Vito Maggiolo, a DC Fire and EMS spokesperson, said.

Lafayette Square, a seven-acre public park that lies directly north of the White House, is often crowded with visitors, especially in the summer months. The lightning struck the four people near a tree that stands yards away from the fence that surrounds the presidential residence and offices.

Temperatures in Washington exceeded 32.2C yesterday, forecasters said. A violent thunderstorm swept through the capital late in the day.

Officers of the US Secret Service and US Park Police, which have a regular presence in the square, went to the assistance of the victims immediately, Maggiolo said.