A second wave of some 30,000 unaccompanied illegal minors from violence-ravaged Central American nations is expected to swamp the U.S.-Mexico border in September and October, a crisis that could be worse than the one that has already pushed 62,000 children into the U.S., according to a top immigration group.

“Right now it’s just too hard for them to cross, but we expect when it cools down a little bit in August or in September, October, we’ll see another surge again,” said Tiffany Nelms with the U.S. Committee for Refugees and Immigrants, a key support group handling the current crisis.