Much of the world’s water resource infrastructure was designed for specific regional snowmelt regimes under the assumption of a stable climate. However, as climate continues to change, this infrastructure is experiencing rapid regime shifts that test design limits. These changing snowmelt cycles are responsible for extreme hydrologic events occurring across the Contiguous United States (CONUS), such as river flooding from rain-on-snow, which puts infrastructure and communities at risk. Our study uses a new spatial snow regime classification system to track climate driven changes in snow hydrology across CONUS over 40 years (1981 – 2020). Using cloud-based computing and reanalysis data, regime classes are calculated annually, with changes evaluated across decadal and 30-year normal time scales. The snow regime classification designates areas across CONUS as: (1) rain dominated (RD), (2) snow dominated (SD), (3) transitional (R/S), or (4) perennial snow (PS). Classifications are thresholded using a ratio of maximum snow water equivalent (SWE) over accumulated cool-season precipitation, with a comparison of two approaches for selecting maximum SWE. Results indicate that average snow cover duration generally became shorter in each decade over our evaluation period, with rates of decline increasing at higher elevations. Anomalies in SD spatial extents, compared to the 30-year normal, decreased over the first three decades, while anomalies in RD extents increased. Also, previously SD areas have shifted to R/S, with boundary lines moving up in latitude. As water managers adapt to a changing climate, geospatial classification, such as this snow regime approach, may be a critical tool.