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

If the value is 10 or more ACE away from one of the cutoff values, this market resolves in January 2025 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: 2020
Near normal: 2017, 2019, 2021
Above normal: 2014, 2015, 2016, 2022, 2023
Record high: 2018

The least active season in recorded history was 1977, while the most active season was 2018.

See also my El Nino / La Nina market for hurricane season: https://manifold.markets/SaviorofPlant/will-it-be-el-nino-la-nina-or-neith. La Niña tends to suppress Pacific tropical cyclone activity, while El Niño tends to enhance it.