Discharge data and in-stream temperature for a peatland headwater stream of the Conwy catchment, North Wales are presented from March 2008 until July 2011. The stream for which the data represents is the Nant y Brwyn situated on the Migneint blanket bog within Snowdonia National Park. The purpose of the data is to calculate annual run-off estimates for the Nant y Brwyn catchment and to provide support for estimating fluvial carbon fluxes. Note: there are gaps in this data set due to equipment/battery failures and/or freezing of the stream. Note dates added to dataset name on 22/06/2017