Abstract:The Lake Tahoe Basin of California and Nevada is a popular destination for visitors. As temperatures rise globally, visitation to this climatic refuge is likely to grow. Increased visitation contributes to increases in vehicle miles of travel (VMT), congestion, crashes, emissions, and deteriorating travel experiences at Lake Tahoe, while also contributing to friction between visitors and residents. Policymakers are exploring ways to mitigate these problems, but one key uncertainty to first address is exactly how many visitors are in the Tahoe Basin at a given time and how and where they travel while there. It is also unclear how visitation is influenced by heat in the nearby lower-elevation population centers during the summertime, which is when visitation is the highest. This study thus seeks to 1) quantify day and overnight visitors in the Tahoe Basin, 2) estimate VMT attributable to each group, and 3) model the influence of hot temperatures nearby on visitation and VMT within the Tahoe Basin. We use existing survey data, network GIS analysis, and publicly available weather data to model the relationship between particularly hot conditions and vehicle flow through two of the region’s primary entry points and estimate in-basin VMT attributable to travel through them. We evaluate several ways of defining “hot conditions” nearby and find that between 500 and 1,200 additional vehicles enter the basin at these two points alone, generating an additional in-basin daily VMT of about 12,000 to 33,000 when hot conditions exist. Quantifying the magnitude of the challenge enables managers to design and scale interventions to mitigate impacts.