Landsat scenes spanning 1978–2001 were used to classify thermokarst lake area and determine changes in lake coverage on the Tuktoyaktuk Peninsula in northwestern Canada. Changes in total lake area between scenes were substantial, spanning a 14% increase and 11% decrease, mostly owing to changes in the area of lakes >1.3 km2 in area. Increases in total lake area occurred primarily between 1978–1992, and decreases between 1992–2001. Differences in total lake area between scenes from different years depend strongly on cumulative precipitation in the 12 month period preceding scene acquisition (r2 = 0.82), and not on summer or mean annual air temperature (MAAT). Our results indicate that precipitation is the primary factor influencing the areal extent of lakes as detected by remote sensing. On the Tuktoyaktuk Peninsula, persistent lake area changes (if any) such as might occur by regional warming or changes in evaporation/precipitation balance over decades, are well-masked by short-term climatological changes.