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Comment by jondcallahan | Hacker News Reader

I made a small little web app calculator for myself and my family to figure out how long we could stay outside without needing sunscreen based on current UV and skin type. I use it daily in the summer and a couple thousand people use it every month also. You can check it out at https://sunburntimer.com. It's also free and open source software, github link in footer.

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It would be useful to have an option to change the time of day, rather than always using the current time; e.g. for planning at night what to do tomorrow.

I came here to post this so glad I'm not the only one looking for specific time of day. Or at least give the user the estimated time they can be outside before getting burned? The timer feels great to fire and forget but I might want to plan and I couldn't figure out from the UI what the duration is "safe"

It looks like the "Skin Damage Over Time" chart is the same information as the timer.

This is neat if you are avoiding the "getting red". My understanding is that the damage occurs with or without the sunburn but maybe this goes without saying.

Denver, CO, USA resident here -- this looks _super_ useful and I'm likely to start using it heavily. Our weather here is usually very outside-encouraging (if getting hotter over the years) and our UV is _ridiculous_; I see the index hit 11 and 12 with some regularity. Thanks for the link!

laughs in Australian

https://www.bom.gov.au/climate/maps/averages/uv-index/?perio...

The map isn’t too far off for July[1] considering how far Australia is from the Equator[2].

My area is similar to Sydney in your map. For Denver it’s the elevation that’s exposing them to more UV rays.

[1]https://www.epa.gov/sunsafety/sun-safety-monthly-average-uv-...

[2]https://www.reddit.com/r/MapPorn/comments/cd1t54/relative_la...

Yep, this—we aren’t as close to the equator, but there’s less atmosphere to filter UV. Not so much in terms of beach days, of course, so sunburns here tend to be less than full-body.

All that said: a daily mean of 13-14 is past what we’d see here—and yeah that is some serious burning.

Awesome project! I wanted its Home Assistant equavelant and there's an official integration for it: https://www.home-assistant.io/integrations/openuv/

Looks like the weather might be a bit off, I imagine from your upstream provider. In Indianapolis, all stats look correct except it says we have thunderstorms. Couldn't be a clearer day and nothing on the radar.

This is a clever idea.

Unfortunately, UV exposure is cumulative. So your skin is still getting damaged by the UV rays even if you're not getting burnt.

Cumulative but with a repair mechanism. There's not necessarily "rollover exposure".

There are temporary as well as permanent effects and the repair mechanism can be overwhelmed: photoaging, age spots, mutations.

Right but there are common precautionary rule-of-thumb heuristics which lead normal people to believe that every sun exposure brings them a little closer to death. That's exaggerated. Or at least, the claims are widely contested.

Lets be honest here, every additional sun exposre means you lived longer which directly leads you closer to death sooooo ;P

That part really is cumulative

So how many Joules can you safely sustain in say, a month, or a lifetime ?

I don't think it's really helpful (nor possible) to get into this level of specificity.

Generally, just apply sunscreen and limit prolonged sun exposure when possible (particularly when UV index is high).

Avoiding sunburns (i.e. prolonged sun exposure, particularly when skin is unprotected) is probably the main thing to focus on as I believe studies have shown there is a high correlation between getting burnt and developing skin cancer.

Amazing idea! A little Feedback: I tan easily but still have freckles.

This is awesome thank you for making this!

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