Basically this is a mod that just makes it snow on Fall 28th. The idea was taken from Rune Factory Frontier where it snowed on the last day of Fall, which would explain why the town was blanketed in snow come Winter 1st. Download: http://www.nexusmods.com/stardewvalley/mods/486/? That's pretty much it. Have at it!
Fall 28 Snow Day 1.4 is now available! Release notes: Updated for SMAPI 2.0 (still compatible with SMAPI 1.15). Internal refactoring.