Afternoon showers and thunderstorms made tricky launch and landing weather for STS-105. The Space Shuttle Discovery lifted off from Pad 39A at the Kennedy Space Center one day later than planned. Thunderstorms delayed liftoff for a day and nearly scrubbed the launch on 10 August 2001. Landing on 22 August was delayed one orbit because of rain showers in the vicinity of the Shuttle Landing Facility (SLF).

Thunderstorms formed during the afternoon of 9 August inland from the Kennedy Space Center (KSC). Although no rain was reported at KSC, thunderstorms were close enough to the Return-To-Launch-Site (RTLS) emergency landing approaches to halt the launch countdown. In addition, the anvil cloud from the thunderstorms had moved overhead of both the SLF and the launch pad violating both the Flight Rules for emergency landings and the Launch Commit Criteria.

On 10 August showers and thunderstorms had again formed inland from KSC, but areal coverage was slightly less prior to launch time. Primary concerns for launch weather were an approaching thunderstorm anvil cloud from the south and showers that could possibly develop just inland from KSC inside the RTLS approach corridors. At the 2110 UTC launch time no showers or thunderstorms were observed within 20 NM of the SLF. The forecast for RTLS landing time (about 25 minutes after launch) included showers within 20 NM of the SLF, but that some of the approach corridors would be clear of showers. Showers did develop post-launch and one lightning strike was observed 19.2 NM from the SLF from a brief thunderstorm. By the possible RTLS landing time of 2135 UTC showers were located 8 to 9 NM from 3 of the possible landing approach paths. Should an RTLS landing have been required, the shuttle would have experienced no weather threats to landing.

The 22 August landing was waved-off one orbit because of a small shower that blocked the approach path to runway 33 at the SLF. The two-mile diameter shower was the only one in the entire state of Florida at the time and was located near the Vehicle Assembly Building at KSC right at the decision time for de-orbiting. Very light rain showers and cloudiness occasionally obscured the runway for much of the morning. By the second de-orbit and landing opportunity the small showers and cloudiness had cleared off enough for the landing decision to be made. Briefly after the de-orbit burn some sprinkles and a cloud ceiling developed in the vicinity of the SLF, but the astronaut pilot flying weather reconnaissance confirmed the forecast of improving weather conditions. No sprinkles were located within 30 NM of the SLF and the only low clouds were inland from KSC as Discovery landed at 1823 UTC.

The lead forecaster for the STS-105 mission was Tim Garner. Assistant lead was Dan Bellue. Tim Oram coordinated weather computing systems support as lead Techniques Development Meteorologist for the mission. The next mission, STS-108, is scheduled for liftoff no earlier than 0105 UTC 30 November 2001.