This study presents an integrated spatio-temporal framework jointly characterising seasonal offshore wind-powered green hydrogen supply, HGV freight demand, and hydrogen refuelling station (HRS) system modelling for Portsmouth, UK, projected to 2050. Monthly Weibull wind speed distributions, validated against UK Met Mast observations (r = 0.95, RMSE = 0.52 m/s), are integrated with a full HRS system model. Results reveal a pronounced seasonal supply–demand mismatch: Winter and Autumn generate hydrogen surpluses of 27 and 4 tonnes respectively, while Spring and Summer produce deficits of 10 and 27 tonnes, driven by the inherent seasonal asymmetry of the offshore wind resource. The framework incorporates a three-state dynamic pricing mechanism yielding seasonal hydrogen prices ranging from £2.70/kg to £4.71/kg across three scenarios, with sensitivity analysis confirming electrolyser utilisation as the dominant pricing factor. The framework provides quantitative guidance for HRS developers, fleet operators, and policymakers advancing UK net-zero and Clean Power 2030 targets.