Clathrate hydrates are crystalline solids distinguished by their capacity to host many guest molecules. Natural gas stored in hydrate form, also known as solidified natural gas, is gaining popularity considering its non-explosive nature, long-term storage capacity, and high energy density. Wet substrates of high specific areas with abundant pores are widely used for hydrate synthesis. Here, we investigate the hydrate morphologies and kinetics of pre-humidified activated carbon (AC) systems. Inspired by the hydrate-favorable environment of natural permafrost, we subjected water-containing activated carbon samples to freezing pretreatment. Intriguingly, the resulting hydrates exhibited a novel fiber-dominated growth pattern, without an (or with a negligible) induction period. The effects of water content, carbon particle size, and pressure driving force were comprehensively evaluated to determine the optimal hydrate kinetics. Utilizing the combined effects of ice induction and nanoconfinement, we successfully produced hydrates with an exceptional high methane storage capacity (168 ± 3.54 v/v) using a short duration (90% completion within 30.67 ± 4.25 min), which was achieved in 2.5–3 mm activated carbons with 1.2 water/AC mass ratio using an overpressure of 5.5 MPa. This innovation may represent an important advance that could facilitate the development of solidified natural gas technology.