The California Air Resources Board (CARB) has adopted rules which will require the phase - in of vehicles with enhanced evaporative emissions control features beginning in the 1995 model year. The U.S. Environmental Protection Agency (EPA) is considering similar new requirements. Enhanced evaporative emissions control systems will provide dramatic reductions in this category of volatile organic compounds (VOC) emissions into the environment.One category of evaporative emissions to be measured and controlled under these new requirements is that of running losses. Running losses are those vapor emissions which occur during periods when the vehicle engine is running. As part of the running loss procedure, fuel temperatures are recorded on the test track under specified driving conditions. This report relates the effects of the ambient environment to these two parameters. The collected data are used to recommend a practical approach in order to proceed with the measurement and evaluation of future information.