Atlantic hurricane season officially runs from June 1 through November 30, but Mother Nature does not always follow that calendar – and it looks like this year could also defy the timeline.
In recent days, some forecasting models have hinted at the possibility of a head start to the 2025 season, showing the potential for storm development—specifically in the western Caribbean where conditions appear more favorable.
In seven of the last 10 years, at least one named storm has formed before June 1. For comparison, there were only three years with early named storms from 2005 to 2014.
After six years of storms forming early, the National Hurricane Center decided in 2021 to start issuing tropical weather outlooks beginning May 15—two weeks earlier than previously done.
Some years have even seen multiple prior to the season’s start. There were two ahead-of-schedule named storms in 2012, 2016 and 2020 – and 2020 nearly had three, with Tropical Storm Cristobal forming on June 1.
When a hurricane season starts early, it doesn’t necessarily mean there will be more storms.
But there could be cause for concern this year, as the season’s poised to be a busy one, with an above-average 17 named storms predicted, according to hurricane researchers at Colorado State University.
Early activity has largely been thanks to unusually warm waters in the Atlantic, Caribbean or Gulf basins during the spring. It’s a trend meteorologists and climate scientists have been watching for years.
As our climate continues to warm, so do the oceans, which absorb 90% of the world’s surplus heat. That can have a ripple effect on tropical systems around the globe.
Warm water acts as fuel for hurricanes, providing heat and moisture that rises into the storm, strengthening it.
The hotter the water, the more energy available to power the hurricane’s growth. And a warmer atmosphere can hold more moisture, which in turn means more fuel for the tropical systems to pull from.
Sea surface temperatures are already incredibly warm for this time of year, especially in the Gulf and southern Caribbean. This means any system passing through those regions could take advantage if other atmospheric conditions are favorable and develop into an early named storm.
In the Caribbean, water temperatures are among some of the warmest on record for early May, and more in line with temperatures found in late June and July.
The Eastern Pacific hurricane season has also seen some preseason activity in recent years, though not as frequent as the Atlantic.
Part of the reason is because the Eastern Pacific season begins two weeks earlier, on May 15. In the last 20 years, the Eastern Pacific basin has only had three named tropical systems prior to that date—Andreas in 2021, Adrian in 2017 and Aletta in 2012.
Another reason is the relationship between the two basins and storm formation. Generally, when the Atlantic basin is more active, the Pacific is less so due to a number of factors, including El Niño and La Niña.
For more CNN news and newsletters create an account at CNN.com
