The Nottinghamshire player, who is currently with England's limited-overs side in New Zealand but is not included in the Test squad, will arrive in South Africa on February 25th and remain available until the final of the competition on April 7.
The news is a boost for the 28-year-old who was one of those affected by Nottinghamshire's decision not to allow their players to go forward to the Indian Premier League auction.
Unlike that event, the South African T20 league does not clash with the county season.
"I'm very excited to be joining the Chevrolet Warriors," Patel said.
"I've heard fantastic things about the team and the area. The Warriors have a history of doing well in this format and I hope I can add something extra and make this year a winning season.
"I want to thank my county in England for releasing me to play and, speaking to the staff at the Warriors, I really can't wait to start."
Even if Warriors make the final, Patel would be expected to be available for the first game of the county season on April 10.
Nottinghamshire director of cricket Mick Newell said: "We're happy for him to go, we actively encourage our players to take part in tournaments around the world as long as they don't conflict with the English county season."