Last winter snow fell at the lowest elevation ever recorded in the state of Hawaii, with accumulation occurring on February 9-10, 2019 as low as 6,200 ft. Snow is not actually that unusual at the highest peaks in the state, specifically Mauna Kea (~13,800ft) on Hawaii, where the very high elevation can cause dramatic differences in temperature from what is observed on the shoreline, but is unusual on Maui's largest peak Haleakala (10,000+ft). (I learned about the temperature difference the hard way when I went camping on Haleakala in January a few years ago with gear better suited to the 74 degree F weather we experienced when we left the beach).
However, last winter's storm was very unusual in that the previous lowest elevation snow was observed at was 7,500ft in 1952. According to an article on the storm, most storms in Hawaii are caused by low pressure systems from the SE or SW which bring warmer air from the direction of the equator, whereas last year's storm followed an unusual trajectory and brought cold air from the northern Pacific.
Picture: Snow at Polipoli Spring state park on Maui
Source: Hawaii News Now: https://www.hawaiinewsnow.com/2019/02/11/snow-blankets-hawaii-summits-amid-powerful-winter-storm/
Other sources cited: Caroline Floyd, "Historic Snow Blankets Hawaii, and other vacation favorites," The Weather Network, February 12, 2019: https://www.theweathernetwork.com/news/articles/historic-snow-falls-in-hawaii-first-time-on-record-las-vegas-snow-storm-winter-closes-in-on-vacation-destinations/124248/