When there is a severe enough chance that lightning may strike, the lightning detector sets off a 15 second horn.  (On a side note:  it could be perfectly sunny outside, but if a fast approaching storm is coming it may still go off.  Lightning can strike up to 15 miles ahead of a frontal system.)  This horn will only go off one time as an initial audible warning signal.  Once it is safe to play the all clear horn will sound and the strobe lights will not flash.  The all clear horn will be three * 5 second horns. 

WHEN THERE IS A WARNING, EVERYONE MUST LEAVE THE FIELDS AND
GO TO THEIR CARS.  WAIT IN THE CAR UNTIL YOUR COACH TELLS YOU
EITHER THE GAME HAS BEEN CANCELLED OR IT IS SAFE TO PLAY.

IT IS NOT SAFE TO BE UNDER THE BUILDING OVERHANG, UNDER
THE TREES, OR ON THE SIDELINES.

RECAP
15 SECOND BLAST = BAD
3 - 5 SECOND BLASTS = GOOD