86,400 seconds is treated to cover a day (one day has 24 hours, one hour has 60 minutes and one minute has 60 seconds, so: 1 day = (24 hours/day) × (60 minutes/hour) × (60 seconds/minute) = 86400 seconds/day.
Thus, if Earth is struck by 100 lighting strikes each second, a total of 8,640,000 (86,400 x 100) lightnings will strike the planet in one day.
According to UCAR.edu, recent satellite data suggests that there are more than 3 million lightning flashes worldwide per day, or more than 30 flashes per second on average.
This includes flashes within or between clouds as well as flashes extending from cloud to ground. The amount of lightning found by satellites is considerably less than scientists once thought existed across the planet.
A typical lightning flash contains about 30,000 amps and 300 million volts. This compares to a standard household current of 15 amps and about 120 volts. Typically, a lightning flash is only 1 to 2 inches wide. The step leader that initiates the lightning flash propagates downward from the cloud at a rate of about 320,000 ft per second or about 220,000 miles per hour.
The return stroke (the current that cause the visible flash) moves upward at a speed of about 320,000,000 ft per second or about 220,000,000 miles per hour (about 1/3 the speed of light). In comparison, the sound of thunder travels at about 1100 ft per second or about 750 miles per hour.
See more lightning facts at Maine.gov and NOAA.gov.
Reduce your risk of being struck by lightning while indoors with CDC.gov's Lightning Safety Tips.