The 2025 North Atlantic hurricane season closed with an unprecedented proportion of the most severe storms ever recorded, intensifying concerns about climate-driven extremes, according to data from MS Amlin.

Sam Phibbs, MS Amlin’s head of catastrophe research, said the headline storm count disguised far more worrying signals. “On paper, this year’s Atlantic storm season appeared relatively benign. The total number of named storms and hurricanes fell below both forecasts and the long-term average. Yet 2025 will be remembered for the unprecedented share of storms reaching high intensities.”

He pointed to Hurricane Melissa as the defining event: “Hurricane Melissa was the most powerful storms ever recorded, striking Jamaica with devastating force. Sustained winds reached 185mph, making it the joint second strongest hurricane on record.”

He added that Melissa “was not an anomaly but a warning of the supercharged storms we are likely to face more often in a warming world”, noting its rapid intensification, “with winds doubling from 68mph to 139mph in a single day”.

“This season also saw an extraordinary proportion of storms reach Category 5 status, defined by winds above 157mph. A staggering 60% of hurricanes hit the top of the scale – the highest share on record,” he explained. This aligned with projections that climate change was pushing more storms to extreme intensity.

Although the US avoided direct hurricane strikes, Phibbs cautioned against complacency. “No hurricanes made landfall in the US this year. However, this is down to luck rather than any long-term trend. The season should serve as a cautionary tale: our research indicates insured losses from US hurricanes could rise nearly 50% under a 2°C global warming scenario.”

He warned that warmer waters would allow storms to retain severe strength further north, increasing risks for cities along the upper East Coast. “There is a compelling case for stronger building codes across the Northeast and mid-Atlantic,” he said, calling for standards similar to those in Florida and Louisiana.

The data suggests that more Category 4 and 5 storms could maintain strength further north. MS Amlin projects insured loss increases of about 44% in Florida, 64% in New York and more than 70% in Rhode Island and Massachusetts. A repeat of the 2022 season, which caused US$62bn in insured losses, could exceed $90bn under a two-degree warming scenario.

---