Democrats Barack Obama, Bill Clinton and Jimmy Carter and Republicans George H W and George W Bush are putting aside politics in contrast with President Donald Trump, who has vowed to help Texas and Florida for as long as it takes but has criticised Puerto Rican leaders while suggesting aid there won't be unlimited.
Having so much ex-presidential power in one place is unusual. George H W Bush spokesman Jim McGrath said all five of tonight's attendees haven't been together since the opening of the George W Bush Presidential Library in Dallas in 2013, when Obama was still in office.
The concert features the country music band Alabama, Rock & Roll Hall of Famer 'Soul Man' Sam Moore, gospel legend Yolanda Adams and Texas musicians Lyle Lovett and Robert Earl Keen.
It's happening at Texas A&M University's Reed Arena in College Station, home to the presidential library of the elder Bush. At 93, he has a form of Parkinson's disease and uses a motorised scooter or a wheelchair for mobility, though he participated in the coin flip at February's Super Bowl in his hometown of Houston.
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George W Bush was Texas governor before leaving for the White House and now lives in Dallas.
"It's certainly a triple, if not a homerun, every time," said Brandon Rottinghaus, a political science professor at the University of Houston.
"Presidents have the most powerful and prolific fundraising base of any politician in the world. When they send out a call for help, especially on something that's not political, they can rake in big money."
But Rottinghaus said those attending Saturday's concert were always going to be viewed more favourably since polling consistently shows that "any ex-president is seen as less polarising than the current president."
"They can't get away from the politics of the moment," he said of current White House occupants. "Ex-presidents are able to step back and be seen as the nation's grandfather."
Shortly thereafter, all five ex-presidents appeared in a commercial for a fund-raising effort known as "One America Appeal." In it, George W Bush says, "People are hurting down here." His father, George H W Bush, then replies, "We love you, Texas."
A website accepting donations, OneAmericaAppeal.org, was created with 100 per cent of proceeds pledged to hurricane relief.
Hurricane Irma subsequently hit Florida and Hurricane Maria battered Puerto Rico, while both affected the US Virgin Islands. Organisers expanded the fundraising campaign to help those storm victims, too.