The fire broke out around 3:30 p.m. at the Pines of Ashton Apartments in the 3200 block of Calumet Drive.
In all, 16 apartments were destroyed, and at least 19 people are homeless.
"It was like a big boom, like an explosion, and then after that it was like a clack," said Jazmin Scott, who lives nearby.
Lightning is listed as the cause of the fire, but the sound of the bolt may also be the reason everyone got out safely.
"My wife called me when the building caught on fire," said Jorge Linarez.
Linarez's wife was sitting in their van across the street with their two young children waiting for the heavy rain to pass before getting out. After seeing the flames, his wife took action.
"She went to the second floor and started knocking on everybody's door," said Linarez.
Neighbors say they had no idea there was a fire until they heard her banging on their door. It helped them to get out fast, and without injury.
The Linarez family lived on the bottom floor. They were told they would be given a new apartment at least for now.
The Red Cross is helping all who were displaced.