The "perfect storm" has hit the Eden district, an official with the Western Cape municipality has said.
"Everything that could go wrong has gone wrong," district community management head Clive Africa told News24 on Thursday evening.
Winds speeds up to 110km/h were recorded on Wednesday evening, fanning fires that destroyed several hectares of veld and about 300 structures.
The Western Cape government estimated that 10 000 people had been displaced due to the blaze.
At least nine people have been killed in the storms and fires in the Western Cape this week. The victims included husband and wife Tony and Madré Johnston and their three-year-old son Michael, Netwerk24 reported on Thursday. They were found outside their house on the farm Kalanderkloof, in the Elandskraal area, between Knysna and George. Police said they had been overcome by smoke.
'All I can remember is how I cried'
In Brenton-on-Sea, which is about 14km from Knysna, roughly 15 homes were destroyed. The area was evacuated on early Thursday morning. It was deserted on Thursday afternoon.
Barbie Verster was one of the few residents left. She removed bushes from her son's property to avoid flare-ups. She said she watched how a house located about 500m away burnt down.
"All I can remember is how I cried. This devastation is absolutely the work of Satan," she said.
Chanel Lotter and Dylan Leech evacuated their home in Brenton-on-Sea on Wednesday. They returned on Thursday morning to find it razed to the ground.
"They clothes on our bodies are the only thing we own," Lotter said.
After they evacuated their home, firefighters helped Leech save a friend in Knysna Heights, a 20-minute drive from Brenton-on-Sea.
"She phone and said she jumped into the pool because everything was burning around her. I knew my bakkie was running on empty, but I had to risk it to save her life," Leech said.
Despite the devastation, Lotter said she was grateful.
"If we have to live in tents the next few weeks, that'll be all right. We can be so grateful: we might have lost a home, but some people lost their lives."
Fires in Knysna were brought under control on Thursday afternoon, with the help of the rain. Flare-ups in Plettenberg Bay damaging about five buildings.
A retired resident of Whale Rock, Plettenberg Bay, who asked not to be named, said they had seen nothing like it before.
"Homes have been lost which have been in families for over three generations. Most people are gathering what's left and heading to family elsewhere in the country."