Winter is brutal for sourdough starters. Cold kitchens slow fermentation to a crawl, while dry indoor heating saps moisture from your culture faster than you'd expect. Most home bakers don't realize their starter isn't dead—it's just dormant, waiting for warmth and food. The Proof Box Solution Sarah Kim, who runs a small bakery in Portland, shared her game-changer: she keeps her starter in her oven with the light on and proof mode set to 75°F. This mimics the warm, stable environment her cultures need without the energy cost of full preheating. She feeds it once daily instead of twice, which reduces waste and prevents the thin, liquid layer (hooch) that forms when starters get too hungry during cold spells. The mistake most people make is abandoning their starter entirely. One week of neglect in a cold kitchen and you've got a fuzzy science experiment. Beyond temperature control, location matters. Move your jar away from windows and drafty areas. A kitchen cabinet, even an unheated one, provides better insulation than a countertop. If you absolutely must store it cold, refrigerate it and feed weekly—but pull it out at room temperature 3-4 days before baking to wake it up.