The Doldrums are regions of the Atlantic and Pacific oceans that have little if any wind.
This was a particular problem for sailors in the past when they depended on the winds to propel their ships, a problem that could be potentially deadly.
The Doldrums are caused by solar radiation from the sun, as sunlight beams down directly on area around the equator.
This heating causes the air to warm and rise straight up rather than blow horizontally.
The result is little or no wind, sometimes for weeks on end.
The Doldrums are located a little north of the equator, but the effects can be felt from 5 degrees north of the equator to 5 degrees south of it.
The trade winds border the Doldrums both to the north and south.
Then there are the prevailing westerlies in the higher latitudes and the polar easterlies near both poles.
The rising moist air in the Doldrums can spawn tropical storms and hurricanes.
Nearly every Atlantic hurricane arises in or near the Doldrums.
The unpredictability of the weather, either no winds or potential hurricanes, made the Doldrums one of the least favorite sailing lanes back when all that ships had to power them across the ocean was their sails.