Why is lightning concentrated over land and uncommon over the oceans?
Lightning is concentrated over land and uncommon over the oceans because daily sunshine heats up the land surface quicker than the ocean. The greatest occurrence of lightning on an annual basis is over the Democratic Republic of the Congo. This country is situated in Central Africa. The highest frequency of lightning occurrence in the U.S is in the State of Florida; this State also has the most lightning strikes.
The least occurrences of lightning are in the Polar Regions. Lightning rarely occurs in the Arctic Ocean and Antarctica, and the aforementioned oceans in general. The reason is that these regions are too cold.
Thunderstorms are rare at latitudes higher than 50 degrees North and 50 degrees South. The production of thunderstorms and lightning is typically from tropical air masses. Approximately 80 percent of lightning occurs over land and 20 percent occurs over the oceans. The temperate and tropical regions globally are the most prone to thunderstorms and by extension lightning.
Lightning can occur within a cloud - intra-cloud. It can also occur between two clouds - inter-cloud. In addition, lightning can occur from the cloud to the ground. Approximately 2,000 people are killed around the world annually from lightning strikes. Lightning also kills wild animals and farm animals such as livestock each year. Approximately 100 people die annually in the U.S. from lightning.