The speed of sound is about 1100 ft/sec or 340 m/sec so five seconds from flash to thunder is a mile away and three seconds is a km
Some processes at work are required to stand down if there's enough static in the air but I think this was a special instrument on site that isn't part of a standard weather station or forecast.
__________________
Genesis 49:16-17
"Well, well!" said Holmes, impatiently. "A good cyclist does not need a high road. The moor is intersected with paths and the moon is at the full."