The Town of Flower Mound’s Parks and Recreation Department as well as the Lewisville Independent School District operate the same type of system at their respective facilities. When the conditions for a lightning strike exist, the Thor Guard System will give a 15-second blast on the horn cluster that can be heard approximately 700 yards away. At the same time, a yellow strobe visible from most areas of the park will activate and stay on until the danger has passed or at least 10 minutes after the last detection of lightning. Once the potential for a lightning strike has passed, the system will activate the horns giving the all-clear signal – three, five-second blasts -- and the strobe light will go off.
However, if weather conditions appear unsafe and the system has not sounded the alarm, common sense should be your guide and activities should cease despite the absence of a Thor Guard warning. Due to the unpredictability of weather patterns, it may be possible for the alarm to sound multiple times within an hour or even sound when there appears to be no danger (i.e. clear skies).
While stopping and restarting athletic activities due to Thor Guard warnings may result in some frustration, it is important to remember that the Thor Guard system’s warnings must be heeded at all times. If the Thor Guard system sets off the alarm on a sunny day, it is not malfunctioning. There is a chance of being struck by lightning if the alarm is not heeded (“a bolt from the blue”).
It is worth noting that many of the lightning deaths and injuries that occur each year are from the first lightning strike from an incoming storm or come from the rear of a storm that appears to have passed through an area.