The mechanistic analysis and design of flexible pavements is very dependent on knowledge of traffic loading, materials, and climatic factors. Seasonal variation of climate factors such as temperature, temperature history, and precipitation affects the subsurface conditions of the pavement layers, including the in situ temperature, moisture content, and state of moisture. In turn, these subsurface conditions have a direct relationship with the pavement strength and stiffness, causing seasonal variations in both strength and pavement layer moduli. Many agencies are now moving toward a mechanistic-empirical pavement design, in which the design inputs include, as a minimum, the seasonal variations in pavement layer moduli. The ability to analytically predict and quantify the climatic effects on pavement strength and stiffness has been investigated by numerous researchers, but few comparisons with measured field data have been completed, because of a lack of pavement sites with extensive arrays of monitoring instrumentation. Detailed is a comparison between field results and predictions obtained from an analytical tool, called the enhanced integrated climate model (ICM). The climatic factors used as inputs into the model include temperature, rainfall, wind speed, and solar radiation. The ICM is used to predict seasonal variations in temperature, moisture content, and layer moduli at two representative flexible pavement test sections at the Minnesota Road Research Project site.