Centuries ago, sailors feared not only the storms, but the silence. Drifting beneath a blazing sun near the Tropic of Cancer, they would find themselves trapped in windless waters, known as the dreaded calms of Cancer. The "calms of Cancer" is a region of light or stagnant winds near the Tropic of Cancer, an area circling the globe at approximately 23.5° North latitude. The calms of Cancer often overlap with the Horse Latitudes, zones known for its calm winds. Historically, sailors dreaded these stagnant zones, as sailing ships could be stranded for days or even weeks without enough wind to move forward.

These calm areas occur due to the global circulation of the atmosphere. Around the Tropic of Cancer, warm air rises near the equator, or the Intertropical Convergence Zone (ITCZ). The air then moves poleward in the upper atmosphere, then sinks around 30° north. This subsiding air creates zones of high pressure, called subtropical highs, which suppress cloud formation and reduce wind activity at the surface. The result: dry, stable conditions with light winds - hence the "calms."

The significance of the calms of Cancer extends beyond ships becoming stuck. These regions are often associated with the formation of the world's deserts, such as the Sahara and Arabian deserts, due to the descending dry air. Also, this area is typically too dry for tropical systems to form.

Jennifer Gray is a weather and climate writer for weather.com. She has been covering some of the world's biggest weather and climate stories for the last two decades.