I posted this on another thread, and thought you might want to see it too.
My 5K letter states it as this:
The race will be held rain or shine. If there is lightning in the area, however, the race will either have a delayed start or depending on the intensity of the weather, cancelled. The determination will be made by the Disney Sports Event staff.
The Walt Disney World Lightning Policy is as follows:
Event operations will shut down when lightning is 6 miles out from the event areas. Event operations will not resume until the lightning is 6 miles out moving away from the event areas. Sports Manager will determine this using the *Flash to Bang Rule* and weather radar. The Sports Manager will consult with the Theme Park and Resort Partners and Walt Disney World Security on a course of action to utilize the operational rain plan, delay the event, or cancel the event.
*Flash to Bang Rule* is applied by measuring the time (in seconds) between a visual lightning "Flash" and hearing the resulting "Bang". This time is then divided by a factor of "5" to obtain distance in miles. For example, 30 seconds between "Flash" and "Bang" divided by "5" equals 6 miles.
Hope that helps!