The concert features the country music band <a href="/music/alabama">Alabama</a>, Rock & Roll Hall of Famer "Soul Man" <a href="/music/sam-moore">Sam Moore</a>, gospel legend <a href="/music/yolanda-adams">Yolanda Adams</a> and Texas musicians <a href="/music/lyle-lovett">Lyle Lovett</a> and <a href="/music/robert-earl-keen">Robert Earl Keen</a>.
The appeal backed by the ex-presidents has raised $31 million since it began Sept. 7, said Jim McGrath, spokesman for George H.W. Bush.
Earlier Saturday, President Donald Trump recorded a video greeting that avoids his past criticism of the former presidents and called them “some of America's finest public servants."
“This wonderful effort reminds us that we truly are one nation under God, all unified by our values and devotion to one another," Trump said in the message.
The last time the five were together was in 2013, when Obama was still in office, at the dedication of George W. Bush's presidential library in Dallas.
There is precedent for former presidents joining forces for post-disaster fundraising. George H.W. Bush and Bill Clinton raised money together after the 2004 South Asia tsunami and Hurricane Katrina the next year. Clinton and George W. Bush combined to seek donations after Haiti's 2011 earthquake.
"It's certainly a triple, if not a home run, 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."
Amid criticism that his administration was initially slow to aid storm-ravaged Puerto Rico, Trump accused island leaders of "poor leadership," and later tweeted that, "Electric and all infrastructure was disaster before hurricanes" while saying that Federal Emergency Management Agency, first-responders and military personnel wouldn't be able to stay there forever.
But Rottinghaus said those attending Saturday's concert were always going to be viewed more favorably since polling consistently shows that "any ex-president is seen as less polarizing 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."
Hurricane Harvey slammed into Texas' Gulf Coast as a Category 4 hurricane Aug. 25, eventually unleashing historic flooding in Houston and killing more than 80 people.
Shortly thereafter, all five ex-presidents appeared in a commercial for a fundraising 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 percent of proceeds pledged to hurricane relief.
Hurricane Irma subsequently hit Florida and Hurricane Maria battered Puerto Rico, while both affected the U.S. Virgin Islands.