The effect of weather on the nation's surface transportation systems touches people every day. Each year 7,000 fatalities and 800,000 injuries involve weather-related adverse road conditions as a factor. These statistics represent about 28% of all highway crashes and 19% of all fatalities. The estimated annual economic cost due to weather-related crashes (deaths, injuries, and property) amounts to nearly $42 billion. Adverse weather has a significant impact on traffic operations and is a challenging issue to traffic engineers. However, there is a perception that traffic engineers can do little to mitigate the effects of weather, which is the result of two main factors: (a) no specific tools are currently available for traffic engineers to assess weather impacts on traffic operations and (b) both traffic and weather data are lacking for traffic analyses. As a result, traffic engineers have little understanding of traffic behaviors due to loss of visibility and traction in bad weather. As more road weather information systems and intelligent transportation systems are deployed and integrated, a large amount of traffic and weather data will become available. Data availability and powerful traffic simulation tools make it possible for engineers to develop and assess weather-specific traffic operations strategies to mitigate congestion in bad weather. The purpose of this study is to use CORSIM (a microscopic traffic simulation model) to illustrate a procedure for assessing benefits of retiming traffic signals in bad weather for both principal arterials and regional networks. Some preliminary findings and gaps identified for further research are also provided.