Hurricane season begins today, and while the outlooks have called for an average season, forecasters are warning that even typical years have the potential to lash coastal states with devastating storms.
Here’s what to expect in the coming months.
How many hurricanes will there be?
CNN tracked two hurricane season outlooks this year: the forecast from the National Oceanic and Atmospheric Administration, which was released last week, and another from researchers at Colorado State University, who have been issuing seasonal forecasts for more than 37 years.
NOAA officials are predicting an average hurricane season, with 12 to 17 named tropical storms, five to nine of which could become hurricanes. They expect as many of four of those could strengthen into major hurricanes – category 3 or stronger.
Phil Klotzbach, a research scientist at Colorado State, said in April his group was predicting a slightly below-average season this year: 13 named storms, six hurricanes and two major hurricanes.
The key difference between tropical depressions, tropical storms and hurricanes lies in their wind speeds and the level of organization within the system.
While a tropical depression represents the earliest stage of cyclone development, named tropical storms exhibit more structure and stronger winds. Hurricanes — the most powerful and dangerous of the three — possess the strongest winds and a well-defined eye, making them capable of causing extensive damage over large areas.
Read more: Hurricane categories and other terminology, explained
How many will make landfall?
None of the seasonal outlooks go as far as to predict how many storms could make landfall in the Caribbean or the US. But history has shown that even in years with average or below-average storms, deadly landfalls are still possible.
Last year, for instance, was an average season, but Hurricane Ian was a catastrophe for Florida. The storm killed more than 100 people when it made landfall in September, devastated the coast around Fort Myers and caused inland flooding that lasted weeks.
Florida was then struck by Hurricane Nicole in November, which tore the beach out from under homes in Volusia County, leaving them teetering on the brink of collapse.
There have been six category 4 or 5 hurricanes to hit the mainland since 2017, the most ever during a six-year period. Climate change, especially the buildup of heat increasing the ocean’s temperature, is leading to a larger percentage of hurricanes reaching the highest categories on the scale – a trend that is likely to continue as global temperatures climb.
What are the environmental factors at play this year?
This hurricane season’s activity will largely depend on two competing factors: El Niño, which inhibits storm development, and near record-high ocean temperatures, which will help fuel hurricanes.
El Niño is characterized by warmer-than-average sea surface temperatures in the tropical Pacific Ocean, and tends to increase upper-level winds over the Atlantic, which disrupt and suppress hurricane formation.
El Niño’s influence on this season is still somewhat uncertain because it is only just beginning to develop. That it will eventually form this year is a “foregone conclusion,” Klotzbach told CNN last week.
But there’s another factor that could negate or even outweigh El Niño’s influence this year: Sea surface temperatures in the Atlantic Ocean are already at or near record-high levels, and in a way that “matches up quite well with what we associate with active Atlantic hurricane seasons,” Klotzbach said.
“If these warm anomalies in the North Atlantic persist through the hurricane season, it has the potential to cause less of an El Niño (wind) shear impact than we normally see,” he said, and that possibility is even showing up in “several climate model forecasts” for the summer and fall.
How is climate change affecting hurricanes?
Hurricanes are natural phenomena shaped by complex atmospheric and oceanic dynamics. But they are now increasingly influenced by human-caused climate change.
As our planet continues to warm due to fossil fuel pollution, the impacts are manifesting in the intensification and altered behavior of these destructive storms. Through a combination of warmer waters, increased atmospheric moisture and rising sea levels, the climate crisis has set the stage for hurricanes to pose unprecedented risks to coastal communities.
What names will the hurricanes have?
The World Meteorological Organization chooses hurricane names and the list rotates every six years. Names are gendered alternately through the season, and the list excludes names starting with the letters Q, U, X, Y or Z. If there are more than 21 storms in a season, the names transition to the Greek alphabet.
Some names are retired after particularly devastating storms. “Ian” and “Fiona” were retired last year, for example, and 96 names have been retired from the list since 1953.
Read more: The fascinating and controversial history behind hurricane names
When does hurricane season really get going?
Hurricanes can form at any time during the warm season and late into fall, but on average they peak in the Atlantic in the early fall – which is also around the time that the strongest storms tend to make landfall in the US.
Hurricane season ends on November 30, though there have been several instances where storms continued to form well after that date. In 2005 – the same year Hurricane Katrina struck New Orleans – Hurricane Epsilon formed on November 29 and dissipated December 10. It was followed by an extremely late-season storm, Tropical Storm Zeta, that formed December 30 and lasted into January.