The Atlantic hurricane season has been labelled “hyperactive” after a lull in activity in August and September.

Five hurricanes – Beryl, Debby, Francine, Helene and Milton – crossed the US continental coastline as this year tied with 1893, 2004 and 2005 for the second most landfalls in a season, according to Colorado State University researchers.

Beryl reached category 5 strength on July 2, the earliest Atlantic hurricane on record to attain that level.

Helene and Milton made landfall about 12 days apart, devastating the southeast US and causing more than 250 deaths and a preliminary estimate of about $US100 billion ($153 billion) in damage.

Helene was also the strongest hurricane to hit Florida’s Big Bend region, coming ashore at category 4 intensity and with wind speeds of about 222km/h.

The researchers say the record warm Atlantic combined with a “cool neutral” El Nino-Southern Oscillation to create broadly hurricane-favourable conditions, but a prolonged lull lasted from August 20 to September 23, which is typically the season’s peak period.

The season overall was “extremely active or hyperactive” based on the National Oceanic and Atmospheric Administration’s accumulated cyclone energy definition.

“Named storm days were slightly above their long-term average, while all other metrics were well above their long-term averages,” the university’s summary says.

The Atlantic hurricane season extends from June 1 to November 30.