Izuku never left his house during winter. You could find him wandering in the streets by summer, or having a drink with his former classmates in a random bar in Musutafu.
By autumn, he would be near a tree, watching the leaves dance as they fall from their home, only to return when another season arrives. And during spring, Midoriya would take care of his flowers, so they could bloom and continue the colorful garden he loved so much. But when the first snowflake arrived, he wouldn't leave home anymore. Why would he?
Everything Deku needed always came to him, in the form of a blonde and muscular "angry goblin." Katsuki could easily heat Deku with his quirk, but that would end up killing him, so his arms were enough to protect his "little broccoli" from the cold breeze that would invade through cracks on the wall or a forgotten window that was still open.
Having Kacchan with him would prevent nightmares from attacking like they usually did — the cold wasn't the only thing that bothered Izuku. Every night he dreamed of a life without Bakugou, one where they didn't go to the beach together in the summer, traded messages of love during Valentine's, or went trick or treating during Halloween, even though they were grown adults already.
And every time, Deku would wake up scared, almost crying, just to smile when he saw that Katsuki was still there, and would always be there for him. For laughs, tears, and the sweat — result from the nights of love they always had. And even after these hot nights, the cold would always come back to annoy Midoriya. But he was relieved.
Bakugou would never leave Izuku's house during winter, because his only duty during the season was to make sure the cold would never hurt his boyfriend.