As Hurricane Isaias approaches the US Gulf Coast and Hurricane Simon strengthens in the eastern Pacific, North America faces two developing tropical cyclone threats against a strikingly different seasonal backdrop. The Atlantic has experienced an unusually quiet hurricane season, while the eastern Pacific has been considerably more active.
How is El Niño influencing the two storm systems?
The contrast is partly explained by El Niño, the natural climate phenomenon that can suppress Atlantic hurricane activity while favouring tropical cyclone development in the eastern Pacific.
But the storms also raise a wider question: how is human-caused global warming changing the ocean and atmospheric conditions in which hurricanes develop?
Both storms remain subject to changing forecasts, however in recent days and hours their force and strength have only become stronger in the recent days than what the original forecasts predicted.
Their development nevertheless provides an opportunity to examine the interaction between natural climate variability and long-term warming—and why a quiet hurricane season does not necessarily mean a low risk of disaster.
The 2026 hurricane season: two oceans, two contrasting patterns
Atlantic basin
Hurricane Isaias – first hurricane of the season.
Eastern Pacific
Above average
More active than usual
Climate driver: El Niño
El Niño generally increases Atlantic wind shear while favouring tropical cyclone activity in the eastern Pacific.
Long-term influence: Ocean warming.
Rising ocean heat content, increased atmospheric moisture and sea-level rise can influence storm hazards, although their effects differ by region and event.
How El Niño is influencing the Pacific and Atlantic profoundly different
El Niño is the warm phase of the El Niño–Southern Oscillation, a natural climate pattern involving changes in sea-surface temperatures and atmospheric circulation across the tropical Pacific.
Its effects extend far beyond the Pacific Ocean.
In the Atlantic, El Niño typically increases vertical wind shear. This means winds at different heights in the atmosphere become stronger or change direction relative to one another, disrupting the organisation of tropical cyclones.
As a result, El Niño years are often associated with below-average Atlantic hurricane activity.
The eastern Pacific frequently experiences the opposite effect. Reduced wind shear can create more favourable conditions for tropical cyclone formation and intensification.
This helps explain why the 2026 Atlantic season has been unusually subdued while the eastern Pacific has experienced more activity than average.
However, El Niño does not determine every storm’s development. Other atmospheric patterns, regional sea temperatures and short-term weather conditions can reinforce or counteract its influence.
Don’t be fooled by the quiet Atlantic Hurricane season
A quieter hurricane season does not mean the atmosphere is incapable of producing a dangerous storm.
Isaias has developed despite the conditions generally unfavourable to Atlantic tropical cyclone activity. Its development demonstrates that seasonal climate patterns influence probabilities rather than dictate individual outcomes.
The temperature of the water beneath a storm is particularly important. A hurricane can draw energy from warm ocean water, and a deeper reservoir of heat can help sustain intensification even when surface waters are mixed by strong winds.
The Gulf of Mexico’s unusually warm waters have been highlighted in reporting on Isaias. Such local conditions can help a storm intensify, although the storm’s ultimate strength also depends on wind shear, atmospheric moisture and other factors.
This is where the interaction between El Niño and climate change becomes important. El Niño can make the atmosphere less favourable for Atlantic hurricanes even as human-caused warming raises ocean temperatures and changes the background conditions in which storms develop.
One influence does not simply cancel out the other.
How it is influenced by climate-warming oceans
Human-caused global warming is increasing ocean heat content and warming the atmosphere. These changes can affect tropical cyclones in several ways.
First, warmer waters can provide greater energy for storm development, provided other atmospheric conditions are favourable.
Second, a warmer atmosphere can hold more water vapour. This increases the potential for heavier rainfall, making flooding a major hazard even when a storm’s wind speeds are not exceptional.
Third, global mean sea level is rising. A storm surge that would previously have reached a particular height can therefore start from a higher baseline, increasing the potential for coastal inundation.
These effects should not be confused with a claim that every hurricane is becoming stronger. Tropical cyclones remain complex systems, and the influence of warming differs between storms and regions.
Nevertheless, research indicates that climate change is increasing tropical cyclone rainfall and the proportion of storms reaching the most intense categories globally. Rising sea levels are also increasing the risks associated with coastal flooding.
The story behind the Atlantic–Pacific contrast
The contrasting behaviour of the two ocean basins illustrates why it is misleading to treat climate change as a simple explanation for every year of extreme weather.
El Niño can suppress Atlantic activity and favour eastern Pacific activity. Climate change is altering ocean temperatures, moisture availability and sea levels across both regions.
These processes operate at different timescales and through different mechanisms. Natural variability can strongly influence a particular season, while human-caused warming changes the longer-term conditions against which that variability unfolds.
The result is not a uniform increase in every type of storm everywhere. It is a changing distribution of risks.
Looking beyond the number of hurricanes
Counting storms is useful, but it does not provide a complete measure of the danger faced by coastal communities.
A season with fewer hurricanes can still include a devastating landfall. A storm’s rainfall, forward speed, storm surge and path across populated areas can matter as much as its maximum wind speed.
Isaias and Simon therefore offer a timely reminder that the relationship between El Niño and global warming is not a simple contest between two opposing forces.
El Niño helps explain why tropical cyclone activity differs between the Atlantic and Pacific. Climate change is altering the environmental conditions in which those storms develop and the hazards they bring to land.
Understanding both influences is essential for improving forecasts, preparing communities and assessing the changing risks of a warming world.
Follow our live blog for frequent updates as the two hurricanes prepare for landfall.
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