How cold has it been in New England recently? Cold enough for ocean waves to partially freeze along the coast of Nantucket Island in Massachusetts.

Photographer Jonathan Nimerfroh captured these unusual slushy waves on February 20th, when the local air temperature reached a high of only 19°F. While freshwater freezes at 32°F, seawater – owing to its salt content – has a lower freezing point of 28.4°F.

To see more images of this uncommon wintry phenomenon, visit the photographer’s website.

Image Credit: Jonathan Nimerfroh