Old Weather is a citizen science initiative that digitizes historical ship logbooks to recover handwritten meteorological and oceanographic observations recorded by naval and merchant vessels dating back to the 19th century. From a GIS perspective, this project generates spatially rich geospatial data by georeferencing voyage routes and associating atmospheric measurements — including temperature, barometric pressure, wind speed, and sea conditions — with precise geographic coordinates and timestamps. Geospatial analysts leverage this recovered data to reconstruct historical climate patterns, enabling robust spatial analysis across maritime corridors that were previously data-sparse or entirely unmapped in existing environmental datasets. GIS technology facilitates the integration of these digitized records into climate modeling platforms, allowing professionals to visualize temporal and spatial trends through advanced mapping techniques, overlay historical observations with modern datasets, and identify long-term climate variability across oceanic regions. The practical benefits include improved accuracy in climate change research, enhanced predictive modeling for extreme weather events, and the enrichment of global environmental databases with high-resolution historical context. For GIS practitioners, Old Weather represents a compelling example of how crowdsourced digitization transforms archival records into actionable, spatially referenced intelligence supporting both scientific research and policy development.