Atmospheric electricity measurements from Lerwick Observatory, Shetland, UK, provide a rare long-term series of hourly Potential Gradient (PG) data during the twentieth century. The Lerwick PG records have contributed to understanding climatological trends in atmospheric electricity. This archive is a subset of the full dataset, and provides monthly mean PG values for each hour of day, derived from summary sheets between 1964 and 1984, capturing typical daily and seasonal variations in PG.