It is the habit most often dropped at the end of summer: the tube of SPF goes into the cupboard with the beach things. The reasoning seems logical: no more beach, no more sunburn, no more need for protection. It rests on a confusion between two different things.
In brief
UVB, the rays that burn, decrease after summer; UVA, on the other hand, are present all year and pass through cloud and ordinary glass. Keeping an SPF on in the morning therefore remains useful at the office near a window, in the car, on a terrace or during your commute. Only a whole day spent away from windows makes it of marginal value.
UVB and UVA: two different stories
UVB are the rays that burn. Their intensity does drop after summer, with the height of the sun. They are what the SPF number measures first.
UVA, on the other hand, are present all year round, from morning to evening, and they penetrate deepest into the skin. They pass through cloud and, the point many people overlook, they pass through glass. According to the Skin Cancer Foundation, ordinary glass stops most UVB, but not UVA.
That is why the UVA symbol in a circle exists on European packaging: it guarantees UVA protection in proportion to the SPF shown. If you don’t know how to choose your sunscreen, that is the mark to look for first.
So, behind a window at the office?
Let’s be honest rather than dogmatic: it all depends on where you spend your day.
| Your typical day | Everyday SPF, outside summer |
|---|---|
| Office by the window, walking or cycling commute | Yes, every morning: the exposure is real even without any feeling of heat |
| Terrace at lunchtime, breaks outdoors | Yes: the accumulated exposure of “small doses” counts |
| Whole day away from windows, underground commute | The benefit becomes marginal that day |
| Regular car use (side windows) | Yes: side windows filter UVA less than the windscreen |
The logic is simple: outside summer, SPF doesn’t protect you from sunburn, it protects you from accumulated exposure, the kind that, over years, marks the skin more surely than a week at the beach.
The real problem after summer: texture
If the habit drops off when the new season starts, it is rarely out of conviction. It’s because the summer sunscreen, thick and designed for the beach, is a nuisance under make-up or in meetings. The solution isn’t to stop, it’s to change format: a light fluid or a day cream with built-in SPF makes the habit invisible in your routine.
And if you are simplifying your routine for the new season, remember the hierarchy of the minimalist routine: if you keep only one product, it is this one. And if it’s the budget that makes you hesitate, a complete routine on a small budget shows where to save without touching the SPF. It is also SPF, far more than any serum, that decides whether the dark spots that resurface after summer will fade or darken.
The honest final word
Nobody will wear SPF 365 days a year with perfect regularity, and that’s fine. The goal after summer isn’t perfection: it’s not going from “every day in August” to “never again until June”. A fluid applied on the mornings you go out is already most of the benefit.
Finally, if you take a photosensitising medicine or are following a course of dermatological care, the exposure guidelines come from your doctor, and they override anything you read here.
Frequently asked questions
Does UV pass through windows?
UVA does. The Skin Cancer Foundation explains that ordinary glass blocks most UVB, but that UVA passes through windows and cloud all year round.
Do you need sunscreen when it’s grey?
Yes, if you go out. The American Academy of Dermatology points out that UV is present whatever the season, and that a large share passes through cloud.
Do you need sun protection in the car?
Yes, if you drive often. According to the Skin Cancer Foundation, the windscreen is treated against some of the UVA, but the side and rear windows filter it poorly.
Which texture should you choose for everyday SPF?
A light fluid or a day cream with built-in SPF, which sits well under make-up. Look for the UVA-in-a-circle mark, which guarantees UVA protection in proportion to the SPF.