Endeavour is back from a series of hydrogen gas leaks for a third launch attempt. But forecasters say there is a 60 percent chance that storms could force a postponement.
Launch manager Mike Moses said Friday that he's not worrying about the weather since there's nothing he can do about it — even if his name is Moses.
"People make a fair bit of fun about my last name being Moses," he told reporters. "I ought to be able to control the weather, but I just can't. So we'll just deal with what we get."
Endeavour should have blasted off to the international space station in mid-June, but was grounded by potentially dangerous leaks of hydrogen gas. Repairs to a misaligned plate on the external fuel tank, which hooks up with a hydrogen vent line, solved the problem.
The shuttle and its crew are set to deliver and install the third and final piece of Japan's $1 billion space station lab, named Kibo, Japanese for hope. The first two sections flew up last year.
Seven shuttle astronauts plus six station residents will make for the biggest crowd ever in orbit.
Five spacewalks are planned during the 16-day flight.
NASA has until Tuesday or possibly Wednesday to send up Endeavour before making way for the launch of an unmanned Russian supply ship. If that happened, the shuttle flight would be off until late July.
Florida's launch weather is expected to improve with each passing day.