Insulated glazing units with gas filled cavities are commonplace in the United States. Climatic pressures should be considered to assess “pillowing” in flat units and the utilization of glass and edge silicone seals in curved and small units. However, the only codified values for climatic loads parameters are presented in the DIN 18008 standard; derived from climatic data from Munich, Germany. United States climates are significantly more extreme, providing a wider range of loads which should be considered for design. The lack of any agreed design values for the United States poses a challenge for designers and the wider industry. This paper proposes a set of design parameters for climatic load assessment in the United States. It explores the statistical basis and methodology for the derivation of the Munich climatic load parameters and applies them to historical climatic data in the United States. The proposed design values for climatic temperature and barometric pressure variations are based representative cities covering 16 ASHRAE climate zones. A study of glass suppliers provides a basis for altitude variation values. A comparison of glass deflections and stresses between the DIN and proposed values for the United States is presented using automated design scripts.