Feeling down in the dumps on a gray, rainy day? You’re not alone.  One of the most significant issues with cloudy days is their effect on vitamin D levels. When the body has low vitamin D levels, it can also contribute to feelings of depression, which is why it is crucial to maintain healthy levels year-round. 

So, can you get vitamin D on a cloudy day? Yes! This guide will help you understand how to maintain healthy vitamin D levels even on overcast days so you can support your overall health and well-being throughout the year. 

One of the best ways to ensure you get enough vitamin D, even on cloudy days, is to track your sunlight exposure. But, How to Measure Sun Exposure? SunSeek’s easy-to-use sunlight tracker can help you record your daily exposure and determine when to get outside. This will help you maintain healthy vitamin D levels and support your overall health and well-being. 

Table of Contents

• Can You Get Vitamin D on a Cloudy Day?

• What Happens to Your Body When You Get Less Vitamin D?

• 6 Ways to Maximize Vitamin D Synthesis on Cloudy Days

• Download Our App to Track your Daily Sunlight Exposure Today

Can You Get Vitamin D on a Cloudy Day?

Yes, you can still get mood-lifting, immunity-boosting vitamin D on a cloudy day. The full-spectrum sun is still behind that gray cloud cover, and the ultraviolet needed to trigger vitamin D synthesis is still evident. It’s still necessary to practice safe sunbathing because it’s possible to overexpose these days. But safe sunbathing doesn’t mean covering your skin with sunscreen. The best sun protection is gradually building your natural sunscreen, melatonin, rather than exposing your skin to the manufactured toxins in many man-made sunscreens. 

Can Vitamin D Help Combat Seasonal Affective Disorder? 

Winter in most parts of the world tends to be the rainy season, with less sunlight and more cloud cover. And the sun barely shows itself in the far north, on the Arctic Circle and above. The lack of sun exposure results in high rates of seasonal affective disorder (SAD), a recurring depression that usually presents between fall and winter. Many people with SAD have insufficient or deficient levels of Vitamin D. Studies show that a one-hour walk outside, even in overcast conditions, will eliminate the symptoms in most people diagnosed with this disorder. The ultraviolet light level was sufficient to stimulate vitamin D production and result in a brighter mood. So the answer to happiness is sunlight - whether yellow or gray...

Why You Get Less Vitamin D During Shorter, Darker Days 

As you might know, sunlight exposure triggers our bodies to produce vitamin D. "Since our skin requires direct sunlight for this process to take place, shorter days can reduce how much vitamin D we produce during the winter months," says Jacqueline Gomes, RD, a registered dietitian based in Warren, New Jersey. "Our vitamin D levels tend to peak in late summer and early fall, so our vitamin D stores can start to deplete just before the winter months." Here's a closer look at how it works: "Ultraviolet B (UVB) rays penetrate the outer layer of your skin and convert a cholesterol derivative into vitamin D3, which then travels to the liver and kidneys to be further processed into active vitamin D," explains Raj Singh, MD, FACP, FASN, a primary care doctor based in Las Vegas. 

Vitamin D created by this process may last at least twice as long in the blood as vitamin D you get from a supplement, according to a 2023 report in the Brazilian journal Revista Paulista de Pediatria. But the weather forecast plays a role. "On a clear day, your skin can produce a substantial amount of vitamin D in a relatively short period," Dr. Singh says. "On a cloudy day, the process still occurs, albeit at a slower rate because clouds filter a significant amount of light." The temperature of your skin might also play a role here. According to Harvard Health Publishing, warm skin produces vitamin D more efficiently than cool skin. This means you'll make more vitamin D on a hot day vs. a cool one. 

Factors Influencing Vitamin D Production on Cloudy Days 

1. Cloud Density 

Not all clouds are created equal. Light, scattered clouds impact UVB penetration less than thick, dense cloud cover. You can still receive substantial UVB radiation for vitamin D synthesis on days with lighter clouds. 

2. Time of Day 

UVB radiation is most intense between 10 a.m. and 3 p.m. Even on cloudy days, outdoors during these peak hours can enhance your chances of synthesizing vitamin D. 

3. Geographic Location 

Your global location affects the angle at which UVB rays hit the Earth. Closer to the equator, UVB rays are more direct and plentiful year-round, making vitamin D synthesis more efficient, even on cloudy days. In contrast, those living further from the equator may find it more challenging to produce sufficient vitamin D, especially during winter.

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What Happens to Your Body When You Get Less Vitamin D?

The Dangers of Deficiency: What Happens When You Don't Get Enough Vitamin D? 

Vitamin D plays a significant role in our overall health. Vitamin D receptors are in nearly all body cells, according to a July 2017 paper in the Annals of the New York Academy of Sciences. The essential nutrient helps regulate the immune system, relax blood vessels, and support heart and bone health, and it may also help prevent certain cancers, according to Dr. Singh and Gomes. Signs of low vitamin D include getting sick more often and feeling tired. 

Over time, not getting enough can lead to a deficiency, says Dr. Singh, which may be linked to long-term health issues such as Increased gut inflammation (such as colitis and gut microbiome imbalance), Decreased bone health, and risk of bone loss (leading to osteopenia and osteoporosis) Increased risk of cardiac problems (due to blood vessel stiffness and worsening of heart failure) Asthma and chronic lung disease flare-ups (likely related to increased inflammation).

Fertility issues Increased pain in people with fibromyalgia and other chronic inflammatory conditions Many people with low levels of vitamin D report symptoms of increased pain, fatigue, bone pain, gait instability due to muscle weakness, muscle spasms, and sometimes tingling and numbness throughout the body, Dr. Singh says.

How Much Vitamin D to Get Per Day

If vitamin D is so important, how much should we get daily? The recommended daily amount (RDA) is 600 International Units (IU) or 15 mcg for adults, per the National Institutes of Health (NIH). Children ages 1 to 18 should get the same amount, while adults over 70 need more—20 mcg (800 ICU) per day.

When to See a Doctor About Vitamin D Deficiency

For most people, vitamin D levels will inevitably dip a little during shorter, darker months—especially if you live in a place with colder weather. Trying some of the above strategies can help even your levels and prepare you for winter. But if you're concerned about vitamin D going too low (or if you notice symptoms like muscle pain, weakness, or tingling in your hands and feet), head to your doctor for a blood test. While your doctor can order blood work anytime, Dr. Singh recommends getting it done at least once a year with your primary care doctor. From there, if the test shows you're low on vitamin D, you can work with your doctor to figure out a treatment plan for you.

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• Can You Get Vitamin D from the Sun Through a Window?
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6 Ways to Maximize Vitamin D Synthesis on Cloudy Days

1. Get Outside Even When It's Cloudy  

The sun's rays are strongest between 10 a.m. and 4 p.m., even on cloudy or rainy days, so aim to get outside during this window to maximize vitamin D production. One way to achieve this is by taking a 20-minute walk during lunchtime, which can benefit your vitamin D production and mental health. Aim to get out at least three days per week. Another tip? Swap out your treadmill time for an outdoor run instead. This can also help raise vitamin D levels, even if you're running in cloudy or rainy weather or wearing long sleeves when it's cool. 

2. Choose the Right Time  

Plan your outdoor activities during peak sunlight hours, usually around midday. During this time, the sun's rays are more direct, increasing the chances of your skin synthesizing vitamin D despite the cloud cover. 

3. Optimize Your Environment  

Arrange your home or workplace to allow as much natural light as possible. Position yourself near windows and open blinds to let in sunlight. This can be especially beneficial for those working indoors for long hours. 

4. Load Up on Vitamin D-Rich Foods  

Finding sufficient amounts of vitamin D in food alone can be challenging but not impossible. Some foods high in vitamin D include: 

Fatty fish

A 3.5-ounce serving of salmon has 526 IU of vitamin D, while light-canned tuna has 269 IU of vitamin D per 3.5-ounce serving. Sardines and herring are also excellent sources of this nutrient. "Add more fish to your weekly menu with options like salmon and sautéed mushrooms for dinner, or a tasty tuna salad for lunch to keep your vitamin D levels up," Gomes says. 

UV-exposed mushrooms

Mushrooms are unique in that they are the only sufficient plant-based source of vitamin D—but only if they're exposed to sunlight rather than grown in the dark. "They are similar to us in that they produce vitamin D when UV rays hit them," Gomes says. Next time you're grocery shopping, look for the brand Monterey Mushrooms, which are grown under UV light. 

Egg yolks

Two large egg yolks have 9 percent of your daily value of vitamin D. Gomes suggests starting your day with a protein-packed egg and mushroom omelet to get in more of the nutrient. 

Milk

Cow's milk in the U.S. is almost always fortified with vitamin D. Some plant-based milk alternatives also have vitamin D added to mimic the nutritional profile of dairy milk. Check the nutrition facts label on your milk to see if it has D. "For a snack, consider a smoothie prepared with a vitamin D-fortified milk or milk alternative," Gomes suggests. 

5. Consider a Supplement  

If you find vitamin D deficient after blood work, your doctor might suggest a supplement. To help restore your levels, you'll need around 6,000 IU of vitamin D3 daily (or 50,000 IU weekly) for eight weeks, per the NIH. Then, once you reach a healthy level, you can maintain it by taking 1,000 to 2,000 IU daily. When shopping for a supplement, look for a brand certified by a third party, like NSF or USP. "Third-party testing indicates that an independent lab with no connection to the brand has verified the supplement quality and accuracy of its labeling," Gomes says.

6. Try a Sun Lamp  

The research on this is limited, but some studies suggest using a sun lamp—which gives off UV rays similar to sunlight—could help you produce more vitamin D. According to an older October 2007 study in Photodermatology, Photoimmunology & Photomedicine, sun lamps can be beneficial for people with fat absorption problems, or those with cystic fibrosis or short-bowel syndrome, who can't absorb enough vitamin D from their diets. 

That said, more research is needed to confirm these benefits fully. Dr. Singh says people living in areas with little sunlight may benefit from using these lamps for short periods. "However, it's crucial to wear eye protection when using sun lamps to shield the retina from harmful ultraviolet rays," he adds. 

BTW, sun lamps (and light therapy, light boxes, and other non-UV emitting devices) aren't to be confused with UV lamps—which do emit UV rays, per the Cleveland Clinic. Light therapy can help ease seasonal affective disorder during the darker months, per the Mayo Clinic. If you want to try a sun lamp, ask your doctor if it's the right move for you, and if they have a specific brand they recommend.

Download Our App to Track your Daily Sunlight Exposure Today

SunSeek App: Your Guide to Vitamin D and Sun Exposure

SunSeek helps you optimize your daily sunlight exposure by tracking and providing personalized recommendations based on your location, skin type, and health goals. The app combines real-time UV monitoring with guided outdoor activities to help you improve sleep, boost energy levels, and maintain optimal vitamin D levels throughout the year. By aligning your daily routine with natural light cycles, SunSeek makes it easy to utilize sunlight's health benefits while ensuring safe exposure through personalized timing recommendations and cloud coverage forecasts. Download our app now to track your daily sunlight exposure.

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