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Comment by Insanity | Hacker News Reader

+1. Also, just to call out, it doesn't need to be _warm_ for you to need sunblock. Even when it's cooler / cloudier out there you can still get skin damage. Look for UV rating rather than temperature. Conversely, it being hot doesn't imply high-UV either.

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I didn't know about the UV index or what it meant until like three years ago. It blows my mind I went that long without understanding. It was actually wonderful to learn that I could just see if I needed sunblock based on a 0-10 scale.

We never wore sunscreen as kids because we didn't burn. I probably have had three sunburns in my life. Learned once I became an adult that that wasn't sound logic...

I think the Apple Watch or the Weather app or something finally taught me UV index about the same time. Has this information always been readily available? Similarly mind blown about it.

In Australia in at least the 00s, possibly the 90s, I remember it being reported during the weather forecast on the 6pm nightly news.

But Australia has always had a famously robust sun health education programme

This was my experience. Years ago I travelled to New Zealand in what would be their spring time. We stayed in Wanaka but also travelled around Twizel, Tekapo etc.

Although it was pretty sunny with clear blue skies, the air temperature was fairly chilly (shirt, jumper and fleece cold - and I'm Scottish so used to cold weather) and I started to burn. I was warned about this, and the probability of high UV exposure at altitude by the locals and family, and was advised to apply a high factor sunblock whilst roaming around the higher elevations of New Zealand's South Island, which I did.

I got the worst sunburn of my life while skiing in Colorado. I wasn’t wearing goggles or anything on my face, and the sun plus the reflection off the snow was brutal. I didn’t notice it when I was out there, but the next morning I wasn’t able to open my eyes. Lesson learned.

I’ve always wondered about this. I have fair skin, and I tend to burn somewhat easily in very sunny environments like the beach.

However, I’ve never gotten so much as a whisper of sunburn / suntan / anything on an actually cloudy day where sun wasn’t hitting me directly. Is the damage a different type that’s imperceptible? Or is this a public health comms strategy where they assume people will see a single cloud in the sky and decide it’s fine to skip sunscreen, so they talk about how you should slather yourself with sunscreen 24/7, even if the sun is obscured?

The damaging part of sunlight is the UV (Ultraviolet) spectrum. This penetrates clouds more easily than the visible-spectrum light.

So sun obscured != low UV. It will block some of it though.

Or your behavior is different on a cloudy day? More covered in clothes, not sitting still in the sun at the beach all day etc.

I’ve gotten visibly sunburned on cloudy/foggy days, where it was completely overcast. You may have gotten lucky.

IIRC, certain types of hazy high clouds can actually make the UV exposure worse. Personally, I got the worst sunburn of my life on a cloudy day.

I think the point is just about temperature. I've experienced this out on lakes in the northern US for example. It's sunny but not like a tropical beach, and maybe even a little chilly. But you'll definitely get burnt without sunscreen

People who are new to skiing/snowboarding are often surprised that their faces get sunburned, because of course it's cold and so how could they get burned

And snow makes it worse by reflecting.

Geography has a lot to do with it as well. Proximity to the equator, altitude, etc.

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