Feeling extra tired during the winter is common. With shorter days and lingering nights, it’s natural for your body to feel sleepier during winter months.

Many of us dread wintertime — with its frigid temperatures and long nights — the bleak days often lend themselves to a generally sense of lethargy. As the season drags on, motivation feels tied to the sunlight and crawling in bed early becomes increasingly tempting.

Feeling sluggish during the winter is common. If you’re fighting an urge to hibernate, you’re not alone. An estimated 10 million Americans suffer from seasonal affective disorder (SAD), or, seasonal depression.

Difficulty waking up and decreased energy levels is a hallmark symptom of SAD. But even if you are not experiencing SAD, feeling extra sleepy during the winter is normal.

Out of the various reasons for wintertime fatigue, here are some of the most common.