Let’s say you counted 18 seconds. To find your distance from the lightning in miles, divide 18 by 5 to get 3. 6 miles. To find your distance from the lightning in kilometers, divide 18 by 3 to get 6 kilometers. Though you won’t be able to get a completely accurate result because the weather may vary in temperature and humidity, which will slightly affect the speed of sound, this is a good way to estimate how far you are from the lightning.
Let’s say you counted 3 seconds. Multiply that number by 340 to get your distance in meters. 3 x 340 = 1020 meters. Multiply that number by 1130 to get your distance in feet. 3 x 1130 = 3,390 feet.
