Season two took months to film in different parts of Canada, including Hamilton, Ontario, and Toronto. In interviews, the cast members said that when they started production on the second season, the weather was extremely warm but cooled down (hence the snow) near the end of filming.
In an interview for MTV News, Gallagher said that shooting the finale was challenging because the weather changed.
"We were in a Canadian summer, which was very hot and humid and we're supposed to be in Dallas, and all of a sudden, winter hits and the entire set is covered in snow," Gallagher explained.
Because there was no way to work around the snow, the show writers incorporated the cold front into the uncontrollable powers Harlan got after Vanya saved his life on episode four.
Speaking to Mashable, Raver-Lampman also said that they finished shooting in November and a snowstorm hit when they had to film the big finale battle.
The snow made it difficult to maintain consistency while filming, since the actors often filmed the same scene multiple times, leading to footprints in the snow. So, in addition to the VFX team working to digitally add snow to hide any continuity errors, the actors also ran on sheets of Styrofoam and white fabric.