(CNN) -- The space shuttle Discovery was waved off from its first chance to land Friday afternoon because of unstable weather near Kennedy Space Center in Florida, NASA said.
The space shuttle's landing in Florida was delayed Thursday, shown. A first attempt Friday was called off, too.
The shuttle will make another orbit of Earth, while NASA mission managers watch to see if extreme moisture and lightning threaten a safe landing.
The next opportunity to land in Florida would come at 7:23 p.m. ET; however, Mission Control told the shuttle crew the forecast for that time "looks about the same."
Crews have been activated at Edwards Air Force Base in California's Mojave Desert in case NASA decides to land the shuttle there, where the weather is not considered an issue. There are two chances to land Friday evening in California.
The space agency, however, usually exhausts all landing windows in Florida before sending the spacecraft to California. A landing on the West Coast adds a week to the turnaround time before the shuttle can be ready for another mission and it costs several million dollars.
The landing could be delayed until Saturday when there are two more chances to land in Florida or California.
Discovery initially was scheduled to return to Earth on Thursday, but poor weather in central Florida also forced a delay.
The seven astronauts are wrapping up a 13-day mission to the international space station, where the crew made repairs and delivered supplies. The crew executed three spacewalks and dropped off a Combined Operational Load Bearing External Resistance Treadmill, or Colbert treadmill. It was named after comedian Stephen Colbert.
Weather and technical problems delayed Discovery's launch three times before blastoff.