LeRoy Cain, chairman of the mission management team, said Saturday there's about a 50-50 chance - maybe a little better - that the weather will cooperate.
"We're always hopeful, and I guess I would call it optimistic," he told reporters.
Mission Control will have Edwards Air Force Base in California, the backup site, ready to support a landing as well, just in case Florida doesn't pan out.
Marginal weather is expected at Edwards on Sunday night. On Monday, conditions are expected to worsen at Cape Canaveral but improve in California. As a last resort, NASA could always consider the White Sands landing strip in New Mexico, used only once for a space shuttle landing, way back in 1982.
Endeavour has enough power and supplies to remain in orbit until Tuesday.
"We're a long ways away, meteorologically speaking, so there are a lot of ways this could turn out," Cain said.
The two-week mission got off to a late start Feb. 8 because of cloudy weather at the launching site.
As of Saturday evening, engineers still were evaluating the data beamed down earlier in the day from the astronauts' shuttle inspection. The crew used a laser-tipped beam to check the wings and nose for any signs of micrometeorite damage.
Two windows suffered small dings from bits of space junk, but posed no concern for re-entry, Cain said. In addition, something small was seen floating out of Endeavour's payload bay early Saturday. It appeared to be a small piece of tubing or some other inconsequential object, Cain said.
Four more shuttle missions are on the books, essentially space station supply runs. The next, by Discovery, is set for early April.
The space station, meanwhile, is virtually complete.