Convincing scientific evaluation, as well as public critique, of the current United States and Canadian weather services' wind chill indices, which are based on the 1945 Siple & Passel Index, led to the services' decision that an upgrade of the indices was needed. This was brought to the attention of the United States Office of the Federal Coordinator for Meteorological Services and Supporting Research (OFCM). OFCM constituted the interagency Joint Action Group for Temperature Indices (JAG/TI) with the purpose of improving the operationally used extreme temperature indices by planning and executing strategies for addressing deficiencies; by reviewing practices and procedures pertaining to the use or development of these indices; and by coordinating any changes to the official indices, including the wind chill indices. The first goal of the JAG/TI was to upgrade and standardize the index used for determining wind chill impact.

The JAG/TI consists of representatives of several U.S. Federal agencies (U.S. Air Force, U.S. Army Corps of Engineers/Research and Development Center/Cold Regions Research and Engineering Lab (CRREL), U.S. Army Research Institute of Environmental Medicine, Department of Energy, National Oceanic and Atmospheric Administration/National Weather Service (NWS), Federal Aviation Administration, Federal Highway Administration, U.S. Department of Agriculture, Department of Energy, and the Federal Emergency Management Agency); the Canadian government (Environment Canada/Meteorological Service of Canada (MSC) and Defence Research and Development Canada/Defence and Civil Institute of Environmental Medicine (DCIEM)); the academic research community (Indiana University-Purdue University in Indianapolis (IUPUI), University of Delaware, and University of Missouri); and the International Society of Biometeorology (ISB). The JAG/TI members and participants agreed to have Mr. Randall Osczevski (DCIEM) and Dr. Maurice Bluestein (IUPUI) develop a new Wind Chill Temperature (WCT) Index and base it on their recently published new wind chill models (Bluestein and Zecher 1999, Osczevski 1995 and 2000). Through JAG/TI workshops, discussions and funded research, Mr. Osczevski and Dr. Bluestein developed, and the JAG/TI members approved, their new WCT Index for implementation. The main environmental parameters in the new wind chill formula are wind and air temperature, as recommended by JAG/TI. Also recommended for inclusion were the effects of solar radiation, which may be added in the future. Based on the review of the science, the JAG/TI determined that the human face was the part of the body most often exposed to severe winter weather, and therefore, should be used as the model for evaluating the wind chill impact. Human studies in a wind and thermal chamber were conducted at DCIEM to verify the accuracy of the new formula. This new WCT Index makes use of advances in science, technology, and computer modeling to provide a more accurate, understandable, and useful formula for calculating the dangers from winter winds and freezing temperatures. This Index was implemented in the United States and Canada by NWS and MSC, respectively, for the 2001/2002 winter season, resulting in a consistent wind chill formula being used in North America.