In fall 2024, as Hurricane Helene and Hurricane Milton battered the southeastern United States, a claim spread online that no hurricane has ever crossed the equator.
An Oct. 1 Reddit post (archived) making the claim, which had more than 103,000 upvotes as of this writing, included a map purporting to show past hurricanes' paths, with a large gap separating those in the northern and southern hemispheres:
"They would have to change their rotation when crossing the equator, and the amount of paperwork required to get permission for that is insurmountable," one commenter joked. "Latin America has 99 problems but hurricanes ain't one," wrote another.
Many Reddit users pointed out that the phenomenon was due to an atmospheric force called the Coriolis effect. In short, the rotation of the Earth influences winds and surface ocean currents. Circulating air is deflected from a straight pattern into a curved path: toward the right in the Northern Hemisphere and toward the left in the Southern Hemisphere.
Snopes found examples of the hurricane claim dating back to at least 2003, with posts suggesting as much having appeared on various social media platforms, including TikTok, X and Quora. A 2023 Reddit post making the claim used an image similar to the one shared in 2024:
No hurricane has ever crossed the equator
byu/not_so_pro_pga inDamnthatsinteresting
Through a reverse-image search, Snopes determined that the graphic above is genuine and was published by NASA Earth Observatory. It showed the tracks of tropical cyclones based on hurricane data available from 1851 through 2006.
Snopes reached out to the National Weather Service, which confirmed the claim that no hurricane has ever crossed the equator is true based on the agency's records.
Hurricanes are grouped into categories, with 3 through 5 being the most severe. In the image, bright red swashes of color indicate where numerous Category 5 storms have traveled over time, while orange and gold lines indicate Category 3 and 4 storms. The blue and yellow paths show weaker Category 1 and 2 storms.
An atmospheric force known as the Coriolis effect prevents hurricanes from crossing the equator. As NASA stated:
The Coriolis force results from the Earth's spherical shape and its rotation. The force keeps air from moving in a straight line across the surface of the Earth. Instead, the Coriolis force spins moving air to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. The Coriolis force is strongest near the poles, and zero at the equator. Although frequent thunderstorms do occur at the equator, the air rushing into the low-pressure centers of these storms doesn't get the needed "spin" from the Coriolis force, and so the storms don't develop the large-scale rotation that sets them on the path to becoming hurricanes.
"The mechanisms are mainly due to the Earth's rotation and the trade winds blowing from east to west about 20 to 30 degrees north and south of the equator. The motion of the trade winds, in combination with the spin of the earth, results in the phenomenon called the Coriolis Effect," the NWS' Maria Torres wrote in an email to Snopes.
"As the warm, moist air from the equator rises in the atmosphere and cools, becoming clouds, it eventually develops into storms in the tropical regions," Torres continued. "The storm will gradually steer away from the equator due to the Coriolis effect."
This steering is provided by a high and low-pressure area in the atmosphere that essentially "steers the tropical cyclones always away from the equator." The Coriolis force is weakest at a latitude of zero — hurricanes cannot form within five degrees latitude of the equator, the National Weather Service explained.