The Frosthawks functioned as a rebellious faction inside the Partisans, until Saw Gerrera, who was their leader, expunged them from the Partisans organization at some point before the Battle of Scarif which happened in 0 BBY.
Their existence was noted in a report presented to Rebel Alliance leader Mon Mothma, which was subsequently preserved within The Rebel Files.
The group known as the Frosthawks receives a mention within the pages of Star Wars: The Rebel Files, a reference work set within the Star Wars universe released in 2017 and penned by Daniel Wallace.