October 2, 1858, marked a challenging day for San Diego. On that particular Saturday morning, just before noon, the city experienced a hurricane of an intensity its 4,300 inhabitants had never witnessed. Despite historical newspaper accounts and weather data classifying the storm as merely a Category 1, it nevertheless delivered a significant impact.
“A formidable gale erupted from the S.S.E. [south-southeast],” reported the Daily Alta California at the time, “and persisted with absolute ferocity until approximately 5 p.m., when it began to subside…It blew with such force, and the atmosphere was filled with such thick clouds of dust, that visibility across the Plaza was impossible…[H]omes had their roofs torn off and were flattened, trees were uprooted, and fences demolished. It is widely considered to have been the most severe gale ever observed in San Diego.”
While the storm was destructive, it was also infrequent. Despite the numerous natural and human-induced challenges the U.S. west coast faces—such as earthquakes, droughts, and wildfires—it typically avoids hurricanes. Even with two tropical systems—hurricane Kiko and tropical storm Lorena—currently active in the Pacific Ocean, neither is predicted to cause substantial damage.
Kiko is advancing westward toward Hawaii, and if it does make landfall, its effects are expected to be limited to delivering “considerable wind and rain to the islands,” according to hurricane specialist Alex DaSilva. Lorena might reach northwestern Mexico and potentially the southwest U.S., also bringing heavy rainfall, along with the increased risk of mudslides in Mexico. These storms, combined with the recent memory of Hurricane Hilary, which caused severe flooding in Baja and Southern California in 2023, might have led some to believe the west coast is turning into a hurricane hotspot. However, these occurrences, though disruptive, do not compare to the devastating impact of major hurricanes—like Katrina, Andrew, and Mitch—that eastern Mexico, the Caribbean, and the southeast U.S. regularly confront during their annual hurricane season. So, what accounts for the Pacific Ocean’s relatively calm nature compared to the Atlantic, which is frequently disturbed by storms?
The disparity in hurricane activity between the two oceans is actually more of a climatological misconception than a reality. Data from the National Hurricane Center and the Central Pacific Hurricane Center indicates that the average Atlantic hurricane season, from June 1 to November 30, records 14 named storms, including seven hurricanes and three major hurricanes (categories 3, 4, and 5). This tally is, in fact, slightly lower than what the Pacific basin experiences during its May 15 to November 30 hurricane season, which averages 15 named storms, including eight hurricanes and four major hurricanes.
“The Pacific is an immensely larger body of water, and a significant portion of that water lies within the tropics,” explains University of North Carolina climatologist Charles Konrad, who directs the . “It serves as the primary breeding ground for what we term tropical cyclones, encompassing both hurricanes and tropical storms. A greater number of them originate there.”
The Pacific’s vast expanse provides ample space for storms to develop and move, and while they capitalize on this—particularly in the tropics—they generally bypass North America’s west coast, often going unnoticed by most Americans. Several factors contribute to this phenomenon.
Firstly, the water in that segment of the Pacific is relatively cool. Along the east coast, the receives a continuous supply of warm water—at least 80°F—which acts as fuel for hurricanes, enabling them to draw moisture and energy from the oceans. Climate change is further elevating these temperatures. For instance, a scorching summer led to Atlantic basin temperatures rising by more than 2.5°F above normal. Conversely, in the coastal Pacific, cool currents flow in from higher latitudes, seldom allowing ocean temperatures to exceed the high 70s.
“We observe a substantial water gyre in all ocean basins,” Konrad notes. “It circulates in a clockwise direction, meaning that for North America’s west coast, the waters during hurricane season originate from the north. This is known as the California current.”
Winds also play a significant role. Low-altitude trade winds typically guide hurricanes in an east-to-west direction. Consequently, the U.S. east coast lies directly in the path of tropical storms and hurricanes advancing from across the Atlantic, whereas the west coast is protected from Pacific storms, which are essentially blown out to sea, sometimes continuing their journey toward Asia.
“The trade winds are situated in the lowest part of the atmosphere, at the surface, and are very consistent,” Konrad states.
Higher-altitude winds over the coastal Pacific can also neutralize hurricanes, blowing from west to east—opposite to the trade winds—and creating turbulence that impedes the storm’s formation. “Our atmosphere is three-dimensional,” Konrad explains. “There’s a wind-shearing effect…that strongly hinders the development of tropical cyclones.”
In recent years, Pacific hurricane activity has been further moderated by more frequent La Niña cycles, characterized by cooler-than-average ocean waters. From 2020 to 2023, there , maintaining a quieter environment along the U.S. west coast.
However, this situation could change. Climatologists are continuously researching global warming’s influence on ocean heating and hurricane generation. While there’s no current consensus on whether this will lead to an increase in storm frequency, it is projected that any storms that do form will be more intense. Nevertheless, one study published in NPJ Climate and Atmospheric Science suggests that over the next decade, the number of Atlantic hurricanes and tropical storms could double compared to the 1970s, while the incidence of storms in the eastern Pacific might increase by a third.
Another, somewhat paradoxical, factor potentially contributing to this rise is our continuously . As environmental regulations reduce toxic emissions from industrial stacks and vehicle exhausts, particulate matter that previously absorbed or blocked incoming sunlight is diminishing, resulting in progressively warmer oceans. “Our atmosphere is cleaner now than it used to be,” Konrad remarks.
Naturally, while human-caused factors are significant, they are relatively minor when compared to the complex natural interaction of wind, water, and temperature that generates storms. As long as this powerful natural mechanism is operational, hurricanes will continue to form. The western U.S. might be spared the most severe dangers, but no coastal landmass located near these storms can ever completely lower its guard.
