Jayden Martell (Aiden) and Lia McHugh (Mia) did activities such as ice-skating, rock-climbing and dinners, to bond in their brother and sister roles. However, the directors kept both of them separated from Riley Keough (Grace), so that they would not grow too close with her.
The painting of Mary seen in the opening scene and throughout the movie is a reproduction of L'Annunciata (Virgin Annunciate) by Italian Renaissance artist Antonello da Messina (1430-1479).
The movies Grace and the children watch at the lodge are The Thing (1982) and Jack Frost (1998), both featuring snowy settings.
Although the film is set in Massachusetts, USA, it was filmed in Montreal, Quebec, Canada. The lodge featured in the film was located on a golf resort, which was closed for the winter season.
Grady the dog is called "Wally" in real life. As of 2024, this film is his only acting credit.