The launch of the space shuttle Discovery was called off today at 1:15 PM local time (EDT) for the second time due to potentially hazardous weather conditions. Liftoff, originally scheduled for 3:26 PM, has been rescheduled for this Tuesday, 4 July at 2:38 PM.

John Shannon, deputy manager of the shuttle program, issued the following statement at a press conference after the most recent delay: "You don't want to get into a rush and do something that's not smart...people won't remember whether the launch was delayed if it is successful, but  if you go into a launch and get struck by lightning, that will be very memorable.''

Indeed, at escape velocity speeds, raindrops become like bullets. As they strike the craft, there is the risk of substantial damage.

NASA decided not to attempt a launch on Monday so the shuttle crew could have a chance to rest. Yesterday's launch was also postponed on account of the weather.

Unfortunately, it is currently thunderstorm season in southern Florida, so there is still a 40% chance that Tuesday's launch may have to be postponed yet again.

The Discovery's mission is scheduled to last 12 days as the seven-astronaut crew ferries 2 tons of supplies to the International Space Station. Up to three spacewalks are planned, and if launch goes as planned, the mission may be extended a day in order to give the crew the opportunity to perform additional tests.

The current "launch window" lasts until 19 July. If Discovery does not launch by then, the whole mission will have to be postponed until August.