It is true that cloud cover doesn’t reduce UV as much as one might think, certainly. But there is a *huge* difference in UV levels between Winter and Summer in Northern Europe. Appopriate levels of sun-cream cannot plausibly be the same regardless of time of year. Time of day also makes a huge difference; if you’re not going outside within 2-3 hours either side of the zenith (in theory noon; in practice moves up to 2 hours off this depending on exactly where you live, local time zones, and daylight saving), you can mostly forget about sun-cream.
There’s certainly a huge difference in the UV levels between winters and summers. Even during winters, if you go out while the UV index isn’t 0, you should wear sunscreen if you’re on tretinoin. (I’m deferring to a dermatologist and haven’t actually checked the sources though.)
It is true that cloud cover doesn’t reduce UV as much as one might think, certainly. But there is a *huge* difference in UV levels between Winter and Summer in Northern Europe. Appopriate levels of sun-cream cannot plausibly be the same regardless of time of year. Time of day also makes a huge difference; if you’re not going outside within 2-3 hours either side of the zenith (in theory noon; in practice moves up to 2 hours off this depending on exactly where you live, local time zones, and daylight saving), you can mostly forget about sun-cream.
There’s certainly a huge difference in the UV levels between winters and summers. Even during winters, if you go out while the UV index isn’t 0, you should wear sunscreen if you’re on tretinoin. (I’m deferring to a dermatologist and haven’t actually checked the sources though.)