Do you need sunscreen every day? Indoors, clouds and winter

Yes, on any day you’re heading outside and the UV index reaches 3, even when it’s gray or cold. No, on a day spent indoors away from sunny windows, or one where the UV peak stays under 3. That second part surprises people, but it’s the line the World Health Organization (WHO) draws in its guide to the UV index. It’s also the rule behind Nubia’s Today, which checks your local UV each morning and marks sunscreen optional only on days the peak stays below 3. Retinoid and acid users, and anyone spending hours outdoors, are better off wearing it on those low days too.

Why bother on ordinary days? Because the evidence for daily use is unusually strong. In the Nambour trial in Queensland, Australia, 903 adults under 55 were randomly assigned to put sunscreen on every morning or only when they felt like it. After 4.5 years, the daily group showed no detectable increase in skin aging, and 24% less aging overall than the when-you-feel-like-it group.

Do you need sunscreen on cloudy days?

Usually, yes. The WHO’s guide says up to 80% of the sun’s UV can get through light cloud, and that haze can even push UV up. You can’t see or feel UV, so a cool, gray morning tells you very little about it. Check the number. Thick cloud does cut UV, sometimes to under 3, and on those days sunscreen really is optional.

Do you need sunscreen indoors?

Not if you’re away from the windows. Glass changes the picture when you sit in direct sun behind it, because it doesn’t stop all UV: in the car study below, side windows let through about 29% of UVA on average, and UVA is linked to cataracts and skin cancer. A desk or sofa in the middle of the room: skip it. A seat in a sunny window for hours, especially if you’re working on dark spots or melasma: wear it.

Do you need sunscreen in the car?

If you drive a lot, yes. When an eye surgeon measured 29 cars in Los Angeles for a 2016 study in JAMA Ophthalmology, the windshields blocked about 96% of UVA on average, but the side windows only 71%, and one let through more than half. The author suggested this may help explain why US drivers have more cataracts in the left eye and more skin cancer on the left side of the face, the side by the driver’s window.

So for long drives, put sunscreen on your face, neck and the backs of your hands. In countries that drive on the left, like the UK, Japan and Australia, it’s your right side that sits by the window.

Do you need sunscreen in winter?

Sometimes, and this is where checking beats habit. The WHO’s guide notes that UV is generally lower in winter, and the farther you are from the equator, the lower it runs, so plenty of winter days peak under 3 and are genuine days off. Snow flips that. The guide says snow reflection can double your exposure, especially at altitude, so a ski trip or a bright, snowy hike is a sunscreen day, with sunglasses and an SPF lip balm too.

Do people with darker skin need sunscreen every day?

Yes, for two reasons. The first is dark spots. The AAD notes that visible light from the sun can cause hyperpigmentation in darker skin, and that sun protection helps dark spots fade. The second is skin cancer. The WHO’s guide notes it’s less common in darker skin, but it does happen, and the AAD says it’s often advanced by the time it’s diagnosed, partly because it can show up where the sun barely reaches, like the palms, soles and nails.

The AAD’s pick for darker skin tones is a tinted, broad-spectrum, water-resistant sunscreen with SPF 30 or higher and iron oxide, which helps block visible light. The tint also helps with white cast, so it’s an easy one to wear daily.

Is it bad to wear sunscreen every day?

It’s a fair question, because plenty of people have been told it is. In an AAD survey of 1,132 US adults in early 2026, nearly half had come across sunscreen misinformation online, including 64% of 18 to 29 year olds, and the AAD estimates more than 16 million American adults have cut back or stopped because of claims they saw online.

The evidence points the other way. Daily users in the Nambour trial aged more slowly, not faster. On vitamin D, a 2019 British Journal of Dermatology review found little evidence that sunscreen lowers it in real life, with one gap worth knowing: the trials used sunscreens of around SPF 16, and high-SPF products haven’t been tested the same way. If a formula irritates you, swap the formula and keep the habit.

What counts as your daily sunscreen?

A real sunscreen layer, with any SPF in your makeup or moisturizer as a bonus on top. On its own, that SPF rarely gets you the number on the label, since you’d need as much foundation or moisturizer as you would sunscreen, and almost nobody wears that much. A real layer means two finger-lengths for your face, and the AAD says at least a teaspoon, a gap the article linked below explains.

Safety note: A new spot, or one that’s changing, bleeding or won’t heal, is worth showing a doctor or dermatologist soon, on any skin tone and anywhere on your body, including palms, soles and nails.