Two collapsed in Miami Sunday, while a third crane snapped in Fort Lauderdale.
Officials with developer The Related Group told the Sun-Sentinel the crane collapse caused no injuries and did not appear to damage anything else.
Miami officials said on Twitter last week that it would take two weeks to move them - and two weeks ago, Hurricane Irma was not even a tropical storm. "Taking them is not something you can easily do".
The Miami-Herald reports that ten years ago Miami-Dade County tried to put in place an ordinance which would require all cranes to be able to withstand 140 miles per hour winds. The tower cranes with a boom on top are created to spin like weather vanes, so they should be stable if Irma strikes, Whiteman said.
Soon after one of the cranes collapsed, the chief executive of the company developing the building told Reuters he was attending the U.S. Open tennis tournament in NY when the accident occurred and had just learned about it.
About 25 cranes remained up before the storm approached South Florida.
Construction sites across Irma's potential path in Florida were locked down to remove or secure building materials, tools and debris that could be flung by Irma's winds.
Carl Roberts has Chinese food, a case of water and a million-dollar view in his 17th floor Gulf front condo - all he needs, he says, to weather the massive storm coming straight at him.
Officials urged people in buildings facing the crane to seek shelter on the opposite side of the building or in a stairwell.
Whiteman said videos of the first collapse posted on social media showed a tower crane that appeared to have lost its jib or boom, though its mast was still standing.
Reporting on the dangers posed by Irma's powerful winds when they reach Florida, NPR's David Schaper spoke to Northwestern University civil engineering professor Joseph Schofer.
A tornado could have ripped the crane loose, Whiteman said.