Locations of focused groundwater seepage to surface water are often hydrologically and ecologically important. Spatially focused or ‘preferential’ seepage can be identified as anomalous cold zones compared to warmer adjacent bank and surface water features (in summer). The temperature of deeper groundwater on Cape Cod is expected to approximate 11 °C year-round, yielding a relatively cold signature where groundwater emerges from the saturated sediment interface. Recent advances in thermal infrared imaging allow efficient real-time scanning for cold anomalies that may be associated with preferential seepage zones, and direct temperature measurements can be collected within the sediments of these zones to better capture the temperature of discharging water. This data release contains locations (GPS), thermal infrared images and derived ‘coldest’ temperature estimates, and direct temperature measurements of collected at possible groundwater seepage zones throughout the upper Coonamessett River bog area (Cape Cod, Massachusetts, 2021). These data were collected on the afternoon of July 29, 2021.