The Iranian government believes that any possible military strike against them will come prior to 30 April 2006 before the weather starts to change in May. The Iranians are prepared though and are confident that any military strike against them will fail with it's objectives.
I'm ex air force. Lot's of low level flying, including over deserts in the summer. Thermals can bring down a low flying aircraft, including cruise missiles. The above statement rings true.
If we are going to do anything before fall, I can easily see how it would need to be before the weather turns against us.