How many times does lightning strike Earth every second?

For most of the twentieth century the textbook answer was 100 flashes a second, a figure worked out in 1925 by counting how many days a year thunder was heard at weather stations and scaling up. It was a reasonable guess with no way to check it.

Then NASA put a lightning detector in orbit. The Optical Transient Detector watched the flashes from above, day and night, over land and ocean, and the total came to about 1.4 billion a year, or 44 a second. The old number had been more than double the truth.

The flashes are not spread evenly. Most happen over land, in the tropics, in the afternoon, and a single patch of the Congo basin and a lake in Venezuela see more than almost anywhere else. The oceans, which cover most of the planet, are comparatively quiet. Lightning likes warm ground.