Over land and during the summer

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This movie shows the location of lightning flashes worldwide over the course of a year. The lightning in the Northern hemisphere is most common in June, July and August, and in the Southern hemisphere in December, January and February. The summer heat provides the energy for lightning. The annual cycle of observed lightning is measured by the space-based Optical Transient Detector (OTD). Notice the annual migration of lightning from the southern to northern hemispheres, with peaks during the hemispheric summer months. Lightning primarily occurs over land due to the strong differential heating and the resultant thunderstorms. Globally, the peak mean annual flash density is over Kamembe, Rawanda with about 82 flashes per square kilometer per year. Over North America, the peak flash density is in the Tampa-Orlando area with 35 flashes per square kilometer per year.

Credit: NASA Lightning Imaging Sensor (LIS) Instrument Science Team and the Global Hydrology and Climate Center located in Huntsville, Alabama

For more info: http://thunder.msfc.nasa.gov