The September 12 fundraiser titled 'Hand In Hand: A Benefit For Hurricane Harvey Relief' will be broadcast on US TV and will be live streamed on Facebook, YouTube, and Twitter.
The relief effort was announced on September 6 and was put together by Houston rapper Bun B and talent manager of Ariana Grande and Justin Bieber -- Scooter Braun.
Initially, the organisers had announced that the money raised during the telethon would be used for the benefit of hurricane Harvey.
"Due to the impending possibility of Hurricane Irma, the Hand in Hand Hurricane benefit has now made arrangements and is prepared to expand its beneficiaries of the September 12th telethon to also include those who may be affected by Hurricane Irma in addition to those affected by Hurricane Harvey," reads the statement by Variety.
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"We are prepared to help in any way we can," it said.
A long list of big-name stars was added to the telethon's lineup of participants on Friday, according to Entertainment Weekly, including Justin Bieber, Drake, Stephen Colbert, Tom Hanks, Tracy Morgan, Nicole Kidman, Catherine Zeta-Jones, Robert De Niro, Jimmy Fallon, and Ellen DeGeneres.
The telethon will air on each of the four major broadcast networks in ABC, Fox, NBC, and CBS; in addition to Bravo, E! Network, MTV, MTV2, MTV Classic, MTV Liv, CMT, and Oxygen.
Multiple charities will receive proceeds from the telethon, including the Mayor's Fund for Hurricane Harvey, United Way of Greater Houston, Feeding Texas, and Habitat for Humanity.
Hurricane Harvey devastated southeastern Texas after it made landfall late last month, leading to catastrophic flooding in the Houston metropolitan area, destroying thousands of homes and causing a total of 70 deaths.