When the weather gets colder and the days get shorter, it is time to make some changes. Entire guides are dedicated to winterizing your home and your car, so why not your health?

When it is time to unpack your coziest sweaters or check your tire tread, winterize your health habits, too.

Watch What You Eat and Drink

Nutrients are particularly important during the winter months when your immune system may be fighting off the flu or other seasonal illness. Winter is also the time when you may not have access to as many fresh fruits and vegetables. Look for seasonal produce and consider supplements or vitamins for what your meals can't provide. Talk to your physician before adding supplements to your diet, and ask specifically about fish oil and vitamins D and C. Eating extra leafy greens and garlic can also help keep your immune system strong.

While you may not be sweating like you do in the summer, your body can become just as dehydrated in the winter. The low humidity in winter dries your skin, and overheated homes and offices dry out your nose, mouth and lips as well. Running a humidifier can help, but drinking lots of water is the best way to stay hydrated and boost your immune system.

Based on a nutrient report from the National Academy of Medicine, the recommended daily intake of fluids is approximately 2.7 liters (91 ounces) for healthy women and 3.7 liters (125 ounces) for healthy men. This recommendation includes total water from all beverages and food each day. If you are physically active, pregnant or breast-feeding, or if you live in a hot climate, you may need to drink more water than the recommended amount.

"Keep a refillable 32-ounce water bottle nearby, which is a great reminder to stay hydrated and mindful of just how much you are drinking throughout the day," says Mohammad S. Bashir, MD, a Northwestern Medicine primary care physician.

Notice Your Sleep Patterns

If the dark mornings are making it harder to wake up, you'll be happy to know your body can benefit from the extra hours of sleep. Healthy sleep is not only good for your overall well-being and a noted mood booster, but it can also keep your immune system strong by giving it enough time to restore and repair itself. Aim for the recommended seven to eight hours for adults but listen to your body when you need a little extra rest.

"Look for the root cause of your sleeplessness," advises Dr. Bashir. "Are you limiting screen time before sleep? Is there a TV in the room? Are you looking at your phone while lying in bed? Is the temperature in your bedroom optimal? Are you drinking caffeine in the afternoon or evening? If none of those apply, then you should talk with your doctor."

With changing light patterns, such as darker mornings and evenings, something else to notice is an alteration in your circadian clock, which can sometimes trigger depression. If your sleep changes drastically or if you start waking up feeling unrefreshed, you may be experiencing SAD.

Pay Attention to What You Are Doing

Getting out of the house is one of the most important components of staying healthy during the winter. That means more than going to and from work — it means keeping up with activities, hobbies and friends. It means exercising, which not only helps you combat stress and burn comfort food calories, but also keeps your immune system in top shape.

"A cost-effective way to get in your aerobic exercise and strength training each week are online classes," says Dr. Bashir. "There are so many resources now available to help you stay active all winter."

Winter can be full of social obligations like holiday parties and family visits, but attending a few big occasions does not provide the same health benefits of seeing people on a daily or weekly basis. Volunteering or joining a class for the winter are just some of the ways you can get social if you're struggling to find motivation on your own.

Winterizing your self-care will not only strengthen your immune system to fight seasonal infections, but it can keep you in a healthy state of mind as well. Spending time outdoors in the sun, staying social, exercising, sleeping and eating well can improve both your emotional and your physical health.