The investigations of hydrogen leakage during the latest decades, have developed our knowledge level. However, few studies concerned the whole dispersion history of the flammable cloud (from generating to disappearing in the atmosphere). A Non Homogeneous Equilibrium Model (NHEM) was used, and validated by a large scale LH2 spill experiment. The predicted data displayed good agreement with the experiment. Moreover, the experiment was further investigated on the colourless flammable cloud. Three primary questions of the hydrogen dispersion process were concerned: the maximum spreading range, the minimum distance above the ground, and the duration time of the flammable cloud in the atmosphere. Three major influence factors were selected to simulate various weather conditions, including ambient temperature (coupled with ground temperature), wind speed and atmospheric pressure. The hydrogen dispersion can be excited with the increased wind speed, and be impeded with the increased atmospheric pressure. The hydrogen dispersion process in four seasons of a year appears a different trend. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.