Kevin Hart is calling on friends to help raise money for Hurricane Harvey victims. In an Instagram video Sunday, Hart told fans he had just been caught up to speed on the catastrophic effects of the storm's flooding and felt inspired to start the Hurricane Harvey Relief Challenge.

"This shit is unbelievable," Hart said. "I think we've participated in a lot of challenges on the internet, some meaningful, some meaningless. But we've all done 'em. I've been a person that's partaken in several of 'em. At this point, I'm going to start a real challenge."

Hart added that he's donating $25,000 to Hurricane Harvey victims and the Red Cross, then issued his friendly challenge. "I challenge The Rock, Steve Harvey, Chris Rock, Dave Chappelle, Jay Z, Beyoncé, Justin Timberlake, Jerry Seinfeld, and I think when you do it, you all should tag somebody else," Hart said Sunday.

Hart gave fans an update on his efforts Monday, promising that a donation link would be live shortly. "My heart hurts for Houston and I truly want to help," Hart said. Hart also announced plans to now donate $50,000 instead of the previously announced $25,000. "I know a lot of my friends will follow," he said.

Other celebrities, including Kelly Rowland and Houston's own Beyoncé, have shared messages of support for Harvey victims:

Harvey, now designated as a Tropical Storm, is expected to remain near the upper Texas coast for the next few days. According to the Weather Channel, more torrential rainfall will likely hit the already flooded Houston area. Total rain amounts of "up to 50 inches" are not improbable.

"In some ways, I think this event is going to far surpass what we saw in Tropical Storm Allison," Dr. J. Marshall Shepherd, head of the atmospheric sciences program at the University of Georgia, told the New York Times Monday.  In fact, Shepherd added, Harvey may go down in history as "the worst flood disaster" ever in the U.S.