Porous safety fences are increasingly being incorporated into the deck furniture at or near the edges of many long-span bridges, and these tall fences (often 3-4 m high) may become blocked during winter storms. The accretion of ice or snow on these fences decreases the porosity and significantly impacts the air flow around the bridge. Due to the relatively low probability of concurring extreme wind and extreme snow/ice events, a methodology is developed and presented to assess the probability of failure due to flutter in these events using wind tunnel test results. Analysis of these test results also indicates that responses due to vortex-induced oscillation may amplify as the fences become increasingly blocked by snow or ice. Similar trends were observed for both single and parallel bridge configurations, suggesting the need for careful studies focused on these effects for bridges in climatic regions susceptible to snow and ice. The effects of snow and ice accretion on fences are also analyzed in the context of design wind loads; results suggest that the primary concern for these effects is the aerodynamic stability of the bridges rather than the increases in wind loading.