The water temperature is measured at a depth of 1 metre, using a StowAway TidbiT temperature data logger from Onset (TBI32-05+37) (https://www.onsetcomp.com/products/data-loggers/tbi32-0537 ). The logger is permanently moored over the deepest point of the lake, and records every 30 minutes. Lough Furnace is a coastal lagoon, protected under the EU Habitats Directive as an Annex I priority habitat (“in danger of disappearance”). This dataset comprises data that have been downloaded, checked and quality controlled. For more recent data, check www.marine.ie. None Suggested Citation: Dillane, Mary; de Eyto, Elvira; Kelly, Sean; Cooney, Joseph; Hughes, Pat; Murphy, Michael; Nixon, Pat; Sweeney, David; Poole, Russell. (2018) Surface water temperatures of Lough Furnace, Co. Mayo. Marine Institute, Ireland. doi:10/cvfv.