Analysis of the climate sensitivity of Rocky Mountain bristlecone pine (Pinus aristata Engelm.) shows potential for developing a multi-millennial-length record of temperature variability. The Upper Rio Grande River basin in the southwestern United States has experienced increases in temperature coupled with persistent drought in recent decades, but the influence of temperature on the frequency and severity of drought, as well as its impact on montane ecosystems remains unclear. This project aim at developing a +2,000 years temperature sensitive chronology augmented with updated and new hydroclimate reconstructions to provides the first insight to how temperatures have changed during extreme droughts in the upper Rio Grande River basin throughout the Common Era. Our approach combines systematic dendrochronological sampling of living and remnant trees with existing collections, micro-climate measurements, and Vaganov-Shaskin process modeling, with instrumental and dendroclimatic analyses to understand the long-term variability in the interactions between seasonal hydroclimatic variables.