For over 1,100 years, humans have recorded information on lake ice cover because of our dependence on ice for transportation, refrigeration, food harvest, and recreation (Knoll et al., 2019; Magnuson & Lathrop, 2014). Two of the longest ice records began for religious purposes: priests recorded and celebrated the timing of lake ice freeze in Lake Constance, Germany (875-present) and Lake Suwa, Japan (1,443-present). In stark contrast to historical patterns, Lake Constance froze for the last time in 1963 and Lake Suwa has frozen only twice per decade since 1988 (Knoll et al., 2019; Sharma et al., 2016). This loss of ice cover precipitates the question, when will lakes experiencing intermittent winter ice cover permanently lose ice? Losing freshwater ice is one of the earliest observed impacts of climate change (Magnuson et al., 2000; Walsh et al., 1998) with far-reaching consequences on the global freshwater supply (Woolway et al., 2020). Recent studies estimated that approximately 15,000 lakes around the Northern Hemisphere may be experiencing intermittent winter ice cover (Sharma et al., 2019) and that the frequency of extreme ice-free years is becoming increasingly common in recent decades (Filazzola et al., 2020). Lakes found in warmer regions, such as along the southern edge of the winter 0 °C isotherm or along continental coastlines, are sensitive to experiencing ice-free winters. In colder climates, deeper lakes were more likely to have experienced ice-free years (Sharma et al., 2019) as deeper lakes take longer to cool in the fall (Brown & Duguay, 2010; Jeffries et al., 2012) and air temperatures need to be below 0 °C for a longer time before deeper lakes freeze (Kirillin et al., 2012; Nõges & Nõges, 2014). Such dramatic loss in lake ice cover underscores a need to identify the most vulnerable lakes before irrevocable ice loss.