The calendar flips from November to December. Daylight gets scarce as days get shorter. Sunshine is replaced with rain and clouds.
For some, the transition from fall to winter can be difficult. Less energy. Lower motivation. More sleeping.
"I think everybody might experience some blues, especially in our area," said Denise Turner, a clinical social worker at Cascade Center for Wellness in Vancouver. "We're not out as much, and sometimes it's discouraging. But sometimes, it's more than that."
For some, the transition leads to more severe symptoms and a diagnosis of seasonal affective disorder.
Seasonal affective disorder is a form of depression that follows seasonal patterns. The more common type of seasonal affective disorder occurs in late fall or early winter. However, some people also experience SAD in the late spring or early summer.
SAD has many of the same symptoms as traditional depression, such as prolonged depressed mood, decreased interest in activities and difficulty concentrating. Unlike people with traditional depression, however, people with SAD tend to eat more, specifically carbs, and sleep more, said Dr. Connie Basch, with Family Medicine of Southwest Washington.
Experiencing depressed mood doesn't necessarily translate to seasonal affective disorder, though. The SAD diagnosis requires at least two occasions of depressed mood that correlates to seasonal changes.
The American Academy of Family Physicians estimates about 4 to 6 percent of people have seasonal affective disorder. Another 10 to 20 percent likely have a milder form of the winter depression, according to the group.
Researchers don't know the exact cause of seasonal affective disorder but point to several possible factors. Among them, shorter days and reduced sunlight, family history and a chemical imbalance.
Physicians and researchers have, however, discovered multiple ways to treat seasonal affective disorder.
Light therapy is a common form of treatment for SAD, said Dr. Mike Lin, with Kaiser Permanente. Light boxes mimic outdoor light, filling a room and requiring only 20 to 30 minutes of exposure each day, he said.
For many people, getting active can alleviate symptoms. Even mild aerobic exercise can get endorphins — the feel-good hormones — flowing, Lin said. Counseling and, in more severe cases, medication are also options, he said.
Some people feel down during the winter months, but that doesn't mean they have seasonal affective disorder, Basch said.
In addition to shorter, darker days, holiday obligations keep people busier than usual, and the consumerism tied to the season creates financial stress for some people, she said.
Unsatisfied expectations can also make people feel down.
"Sometimes, just because everyone else is happy, if they're not happy it can be worse for them," Lin said.
Some simple actions can help fight the winter blues. For example, keep a gratitude journal with things to be thankful for, make time for exercise or take a short vacation, they suggested.
If you can't shake the blues on your own, talk to your doctor, Turner said.
"Take it seriously," she said. "If you catch it and know it, you can manage it."