AbstractDetailed climatic data are essential for analyzing and designing pavements using AASHTOWare pavement mechanistic-empirical design (PMED). Hourly climatic data are used in the enhanced integrated climatic model in the PMED to adjust material properties. The current PMED V2.6.0 has been updated using the North American Regional Reanalysis (NARR) database for rigid pavements and the Modern Era Retrospective Analysis for Research and Applications (MERRA) climatic data for flexible pavements. Because several climatic data sources are available, it is helpful to establish the most viable data in the PMED. In a recent study, the Michigan DOT (MDOT) enhanced the quality of NARR data to improve data coverage and fill data gaps. This paper compares the climatic data for the enhanced NARR stations and closest MERRA-2 stations in Michigan to investigate the differences between the two data sources. The NARR and MERRA-2 climatic data have been validated with the two National Oceanic and Atmospheric Administration (NOAA) stations in Michigan to evaluate the accuracy of the data sources. The paper also evaluated the two data sources for quantifying the effects of climatic inputs on predicted pavement performance. The relative impacts of climatic inputs based on predicted performance have also been documented. The results show that MERRA and NARR climatic data are comparable for air temperature, humidity, and wind speed. Percent sunshine shows a low correlation, and precipitation data is substantially different. MERRA and NARR data quality is similar in Michigan with the NOAA data. In flexible and rigid pavements, performance predictions are substantially different for thermal and transverse cracking, respectively. These differences can be attributed to hourly variations in sunshine data. Temperature and percent sunshine data are the most critical climate inputs for flexible and rigid pavements. Considering the advantages of MERRA data, it is a suitable climatic data source for both flexible and rigid pavements.