Lake Waiau is a small, typically 100-meter-long lake, located near the summit of Mauna Kea volcano, on the Island of Hawaiʻi. It is Hawaiʻi’s only alpine lake and is considered sacred in Hawaiian cultural tradition. Over the past few years, the lake has diminished in size, and, by October 2013, surface water had almost completely disappeared from the lake. In this study, we use high-resolution satellite images and aerial photographs to document recent changes at the lake. Based on our reconstructions covering the past 200 years, the historical lake surface area has typically ranged from 5,000 to 7,000 square meters, but in 2010 a dramatic plunge in lake area ensued. The lake area rebounded significantly in early 2014, following heavy winter storms. This near disappearance of the lake, judging from analysis of visitor photographs and field reports, appears to be highly unusual, if not unprecedented, in the historical record. The unusually low water levels in the lake are consistent with a recent severe drought in Hawaiʻi.