“‘In winter, the sun is harmless’ – this misconception persists stubbornly. However, UV radiation is not a matter of temperature. Studies show that people often confuse the UV index with heat and either overestimate or misinterpret its values, leading to inappropriate behavior ^[1]. The result: unplanned UV doses for the eyes and skin – especially when snow reflects and the air is clear.

UV radiation is invisible; we do not feel it directly – yet it is effective. The UV Indexmeasure of sunburn-causing UV radiation, independent of air temperature indicates the level of exposure. In winter, the sun's altitude decreases, but diffuse and reflected UV components remain relevant. Snow, gaps in clouds, bright facades, and water bodies direct photons our way. It is important to consider the proportion of direct UVradiation coming directly from the sun, diffuse UVradiation scattered by the atmosphere from the entire celestial dome, and reflected UVradiation reflected from surfaces. Protection is successful when we take all three components into account – not just the sunlight from above.

For high performers, winter UV has two consequences: first, cumulative skin damage; second, visual fatigue from scattered light. Models of eye exposure show that the unprotected cornea receives the highest UV doses throughout the day in everyday situations – even when it is cold ^[2]. Regular-sized sunglasses protect only to a limited extent in certain viewing positions, while larger models or ski goggles provide nearly complete protection ^[2]. Shade is also not automatically safe: small, high-mounted canopies primarily reduce direct UV, but allow diffuse and reflected components to pass through – legs and lateral facial areas often remain exposed ^[3]. Measurements of public spaces demonstrate that the protection factor under shaded areas varies significantly and can range from low to very high depending on position and time of day ^[4]. Those who do not understand the UV index use protective measures less frequently or incorrectly – a knowledge issue with practical implications for skin aging, eye health, and daily energy levels ^[1].

Three research strands paint a clear picture. First: Digital 3D models quantify the UV dose at sensitive eye and facial zones. The analyses show that the geometry of eyewear – size, frame, fit – greatly determines protective effectiveness. Large models and particularly goggles achieve almost complete protection; medium-sized forms allow more lateral and diffuse UV to pass. All tested lenses blocked UV in the material, but environmental exposure penetrated through gaps and viewing angles – a crucial practical finding for winter days with significant scattered light ^[2]. Second: Simulations and on-site measurements of shade demonstrate that shade structures primarily absorb direct UV, while the diffuse and reflected components remain variable. Larger, lower-placed structures provide better protection; small, high roofs often deliver only moderate reductions. Under such constructions, legs and peripheral zones are particularly less protected – relevant for walks, playgrounds, and winter outdoor breaks ^[3]. Field measurements in Australian facilities confirm this range with protection factors from about 2 to 16, depending on size, materials, environment, and position under the roof – indicating how important design and positioning are ^[4]. Third: A design index for playgrounds takes into account not only structure type and planting but also the “visible sky fraction” and the direct UV component throughout the day. This approach illustrates which orientation and fabric patterns optimally protect in both summer and winter – and provides a transferable principle for urban winter settings like terraces or waiting areas ^[5]. Together, it becomes clear that winter-appropriate UV protection is less about thick clothing and more about intelligent geometry, viewing angles, and environmental design.

- In winter, wear large sunglasses or ski goggles with 100% UV filters; they significantly reduce the UV dose to the cornea and periorbital areas better than medium-sized models – especially when looking up or in snowy conditions ^[2].
- Pay attention to fit: The closer the glasses sit to the face, the less diffuse and lateral UV radiation reaches the eyes ^[2].
- Use shade deliberately – but correctly: Prefer large, lower canopies or dense tree canopies. Small, high-mounted roofs provide limited protection, especially for legs and lateral facial areas ^[3].
- Positioning matters: Stand in the shade where the greatest shielding is provided between you and the visible sky portion; protection varies depending on the spot under the structure and the time of day ^[4].
- Favor intelligent shade designs: Structures with a low “sky fraction” and appropriate orientation offer better protection throughout the day – even in winter ^[5].
- Check the UV index in your weather app each morning and mentally decouple it from temperature: UV peaks occur around midday, regardless of cold weather. This knowledge enhances the consistent use of protective measures ^[1].

The next wave of UV prevention connects 3D exposure models with practical wearables: personalized recommendations for eyewear shape, shade position, and time of day become realistic [Ref30382242; Ref36789633]. It will be exciting to see how urban planning and shade design indices can be standardized in winter latitudes to create UV-smart public spaces [Ref29878409; Ref23565839].