The Atlantis Space Shuttle launch may not happen on the planned time of 11:26 a.m. ET July 8 due to the weather.

Kathy Winters, shuttle weather officer, said a tropical wave from the Caribbean is expected to hit Florida with a lot of tropical moisture.

The shuttle launch, therefore, has 70 percent chance of canceling on July 8. It has a 60 percent chance of canceling on July 9 and a 40 percent chance of canceling on July 10.

In all, there is a 17 percent chance that it won't launch at all by July 10.

Launch rescheduling, of course, is a common occurrence because having the right weather could literally be a matter of life and death.

A 2007 Associated Press analysis found that only 40 percent of space shuttles launched on time.  Of the failures to launch on time, more than 50 percent of them were caused by technical failures and about one-third were caused by unsuitable weather.

A 1986 Columbia launch and a 1995 Columbia launch hold the joint record of failing 6 times before they finally took off successfully on their 7th tries, according to Space.com.

Failures are expensive for NASA. 

A NASA spokesperson said each canceled launch after the external fuel tank has been loaded costs $1.3 million, reported Space.com.

However, it's still well worth the price to wait for acceptable circumstances before launching.

The 1986 Challenger disaster (which killed 7 astronauts), for example, is likely caused by low temperatures that exacerbated a design flaw in a rocket booster.