I used to keep the curtains closed all winter in my Riverside ranch house. If a covered window felt like a barrier against the cold at night, I figured it ought to stay covered during the day, too. As of mid-September 2026, with winter ahead, I am thinking about that habit again. Here in California, you and I can want warmth from a window and still overlook the part of the day when sunlight can help.
There is a reason closing the coverings can feel like the obvious move. In Riverside, Riverside Public Utilities advises keeping drapes, blinds and shades closed to keep the sun’s rays out in warm weather. I can follow that advice when I want less sun indoors. Winter calls for a different decision: whether to admit the sun while it is there, rather than leaving the curtains in their nighttime position all day.
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What the Department of Energy says
The Department of Energy puts the winter routine plainly: “During winter, open curtains on your south-facing windows during the day to allow sunlight to naturally heat your home, and close them at night to reduce the chill you may feel from cold windows.”…