Transportation systems have become much more vulnerable due to the increased amount of unexpected severe weather events caused by the effects of climate change. One of the direct consequences is that the punctuality of transportation systems is severely affected and the prediction of the on-time performance of scheduled service becomes challenging due to the uncertainty of severe weather's occurrence. The objective of this paper is to investigate two fundamental questions pertaining to the operational reliability of passenger transportation systems, using high-speed rail (HSR) and aviation in China as an example: what are the impacts of severe weather events on HSR and aviation delays, and to what extent are these systems vulnerable to various types of severe weather events? To address these questions, a dataset with 350,000 detailed , on-time performance records of HSR and air services for the period October 2016-September 2017 was adopted. Based on data visualization and statistical analysis, the study reveals that the impacts of severe weather events on HSR and aviation's on-time performance vary spatially and temporally. In general, HSR is less vulnerable than aviation to most severe weather events. In terms of the spatial variation, the operation of HSR in the southeast coastal region is affected more frequently by rain and thunderstorms, whereas the system operated in central-eastern China is more vulnerable to snowstorms.