Activity is tracked in terms of https://en.wikipedia.org/wiki/Accumulated_cyclone_energy. This Wikipedia page has a list of previous North Atlantic hurricane seasons by ACE.

If the value is 10 or more ACE away from one of the cutoff values, this market resolves in January 2026 to whatever value is listed on Wikipedia. If it is close to a cutoff, the market resolves after the reanalysis of all storms is completed (usually in April) to account for postseason adjustments in ACE.

The last ten years had the following activity:
Below normal: 2015
Near normal: 2022
Above normal: 2016, 2018, 2019, 2021, 2023
Hyperactive: 2017, 2020, 2024

The least active season in recorded history was 1914, while the most active season was 1933.