UV Index Guides: Sun Safety, Burn Time & Skin Type
The UV index is a single number, but the useful question behind it changes with who's asking — a parent at a playground, a hiker at 2,500 m, someone three days into a doxycycline course, and someone trying to top up their vitamin D all need different answers from the same forecast. These 16 guides cover the whole spread: what the scale means, how it becomes a burn time for your skin, how to get it onto the devices you already carry, and what changes when your circumstances do.
Understanding the UV index
Start here if the number on your screen doesn't yet mean anything concrete. These cover what the UV index actually measures, how it becomes a burn time for your skin, and why two apps in the same spot can disagree.
UV index guide
What does the UV index mean?
The 0–11+ scale explained band by band, with the burn time each Fitzpatrick type can expect and how altitude, cloud, and reflective surfaces change the dose.
Fitzpatrick skin type quiz
What is my skin type?
The nine-question phototype self-assessment with the scoring rubric, plus a full Fitzpatrick chart and the burn time each type gets at common UV levels.
UV index accuracy
Which UV app is most accurate?
Where UV numbers come from — WeatherKit, NOAA, OpenUV, OpenWeatherMap, WHO — why they disagree by a point or two, and how to sanity-check a reading you don't trust.
Sun exposure tracker
How do I measure my sun exposure?
The four things people mean by tracking sun exposure, the SED dose unit, and how to estimate the UV dose you actually absorbed today.
On your iPhone, iPad & Apple Watch
Practical setup — where to find UV on the devices you already carry, and how to get it onto a surface you'll actually glance at.
How to check the UV index on iPhone
Where is the UV index on my iPhone?
Three methods, from the UV card buried in Apple Weather to a dedicated forecast app that turns the number into minutes.
UV index widget for iPhone
How do I add a UV widget?
Step-by-step setup for Home Screen, Lock Screen, and StandBy widgets, every widget size compared, and what a genuinely useful UV widget should show.
UV index on Apple Watch
Can my watch show UV?
Adding a UV complication to your watch face, which faces suit it best, and how Time in Daylight differs from a burn time.
Best UV index apps for iPhone
Which UV app should I install?
Fifteen apps compared side by side on personalization, forecast range, Apple Watch support, and where each one sources its UV data.
Avoiding — and treating — sunburn
The practical half: how to not burn, and what to do in the first hour if you already have.
How to prevent sunburn
How do I not burn today?
A six-step skin-type-aware routine, a burn-time table across UV 5/7/10, how SPF math really performs in real-world amounts, and spotting a burn early.
How to treat sunburn
I'm already burnt — now what?
First aid that genuinely helps, the popular remedies that don't, a severity table, the day-by-day healing timeline, and the red flags that need a clinician.
When to reapply sunscreen
How often should I reapply?
Where the two-hour rule comes from, the six triggers that reset the clock early, how much product a reapplication really needs, and why reapplying doesn't reset your dose.
Summer UV safety
How bad is peak season?
When UV peaks each day, how high it gets at your latitude, and activity-by-activity risk for beach, boating, alpine hiking, sport, festivals, and gardening.
For your specific situation
The same burn-time arithmetic, tightened or reframed for circumstances that change how much UV your skin can take — or how much you want.
UV index for kids & babies
How much sun is safe for my child?
Age-by-age exposure limits from newborn to teenager, when infants can wear sunscreen, what each UV band means for a child, and when to call a paediatrician.
Photosensitivity and UV
My medication makes me burn faster.
Nine drug classes that shorten burn time, six conditions and procedures that do the same, and the effective-Fitzpatrick shift rule for adjusting while affected.
Vitamin D and the UV index
How much sun do I need?
Why UVB matters and UVA doesn't, why UV below 3 produces none at all, how long each skin type needs, and why the reaction plateaus long before your burn time.
UV index for tanning
When can I tan safely?
The UV 3–5 window that builds colour without tipping into damage, safe session lengths by Fitzpatrick type, and why shoulder hours beat midday.
The thread running through all of them
Every guide here comes back to the same piece of arithmetic. Your skin has a threshold — dermatologists call it the minimal erythemal dose — and UV accumulates against it minute by minute. The UV index tells you the rate. Your Fitzpatrick skin type tells you the threshold. Divide one by the other and you get a burn time: a specific number of minutes rather than a label like “High” that means something different for every person reading it.
Everything else is that calculation adjusted for context — tightened for a child or a photosensitizing medication, inverted for vitamin D, paired with a reapplication timer for sunscreen, or stretched across a season for summer planning. Once the base calculation makes sense, the rest of the guides are variations on it.
Get the burn time without the arithmetic
Sunwise is a personalized UV index and sunburn forecast app for iPhone, iPad, and Apple Watch. Set your Fitzpatrick skin type once and every UV reading turns into a personal burn time in minutes — with hourly and 7-day forecasts, Apple Watch complications, and Lock Screen widgets that keep your remaining safe minutes one glance away.
