Fine-scale assessment of projected future changes in weather and climate extremes in the Chesapeake Bay watershed of the Mid-Atlantic United States

This study investigated the potential shift in future climate including its extremes across the Chesapeake Bay watershed, a region in northeastern United States that is vulnerable to climate change. Using downscaled and bias-corrected projections from 13 CMIP6 Global Climate Models (GCMs) under four Shared Socioeconomic Pathways (SSP126, SSP245, SSP370, SSP585), we analyzed the changes in annual and seasonal precipitation and temperature patterns as well as the change in extreme climate through the evaluation of 20 climate indices.Results reveal a consistent warming trend across all scenarios until the mid-twenty-first century, after which outcomes diverge according to emission pathways. Seasonal assessments showed that average summer temperature will rise substantially in the watershed, especially under the high emissions scenario, accompanied by an increased frequency of heatwaves, tropical nights, and summer days. Concurrently, cold extremes, such as frost and icing days, are projected to decline, especially in northern parts of the watershed. The region is expected to see a decline in icing days by close to 73% by the end of the twenty-first century under SSP585. An increase in the frequency, intensity, and amount of extreme precipitation is also expected.Spatial assessment of the change in climate indices indicated that the watershed's northern and southeastern portions are more vulnerable to these changing extremes. Even the low-emission scenario (SSP126) suggests notable impacts, underscoring the necessity of both mitigation and adaptation. These findings provide crucial insights for policymakers and resource managers seeking to balance ecological protection, agricultural productivity, and community resilience under intensifying climate pressures.