A variety of studies have documented the dangerously high temperatures that may occur within the passenger compartment (cabin) of cars under clear sky conditions, even at relatively low ambient air temperatures. Our study, however, is the first to examine cabin temperatures under variable weather conditions. It uses a unique maximum vehicle cabin temperature dataset in conjunction with directly comparable ambient air temperature, solar radiation, and cloud cover data collected from April through August 2007 in Athens, GA. Maximum cabin temperatures, ranging from 41-76 degrees C, varied considerably depending on the weather conditions and the time of year. Clear days had the highest cabin temperatures, with average values of 68 degrees C in the summer and 61 degrees C in the spring. Cloudy days in both the spring and summer were on average approximately 10 degrees C cooler. Our findings indicate that even on cloudy days with lower ambient air temperatures, vehicle cabin temperatures may reach deadly levels. Additionally, two predictive models of maximum daily vehicle cabin temperatures were developed using commonly available meteorological data. One model uses maximum ambient air temperature and average daily solar radiation while the other uses cloud cover percentage as a surrogate for solar radiation. From these models, two maximum vehicle cabin temperature indices were developed to assess the level of danger. The models and indices may be useful for forecasting hazardous conditions, promoting public awareness, and to estimate past cabin temperatures for use in forensic analyses.