"It is a wonderful day in Maine -- in fact, nice enough for a parachute jump," the nation's 41st president announced on Twitter.
Bush intends to jump from a helicopter with a retired member of the Army's parachute team near his summer home on the Maine coast, spokesman Jim McGrath said.
The announcement was kept secret until the last minute, partly to give Bush himself the option of changing his mind.
"It is vintage George Bush," he said. "It is that passion for life. It is wanting to set a goal, wanting to achieve it. I am sure part of it is sending a message to others that even in your retirement years you can still find challenges."
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The first time Bush jumped from an airplane was when his plane was shot down in World War II over the Pacific. Later, he decided to jump from a plane of his own accord and marked his 75th, 80th and 85th birthdays by skydiving.
During his presidential years, Bush was known for jogging, tennis and fast-paced golf but now uses a wheelchair because of a form of parkinsonism.
Other birthday festivities included a private dinner with more than 200 relatives and friends. His children, including former President George W Bush and former Florida Gov Jeb Bush, will be there, McGrath said.