How to Read the UV Index (and Pick the Right SPF Stick)

By Eugene Kim, Co-founder & Product Lead, HAESKN. Former packaging design lead at Clinique (Estée Lauder Companies). Adjunct professor, Pratt Institute. Reviewed with Sherril HwangBo, Co-founder & Creative Director, former design director at LVMH (Moët Hennessy, DFS).

Published 2026-05-26.

The UV Index is a single number from 0 to 11+ that tells you how strong the sun's ultraviolet radiation is at your location right now. Higher means faster skin damage and faster sunburn. Anything 6 or higher means burn protection is non-optional, and "non-optional" includes reapplication every two hours (EPA).

Most US weather apps show it. Most people glance at it and ignore it. This guide is a practical translation: what each level means, what to do, and what kind of SPF actually holds up at each tier.

The 5 levels at a glance

UV Index | Level | What it means | What to do
0–2 | Low | Minimal danger for the average person | Sunglasses on bright days; SPF 30 if you'll be out 1+ hours
3–5 | Moderate | Stay in shade near midday | SPF 30+ broad spectrum, water-resistant if active
6–7 | High | Damage clock is fast | SPF 50, reapply every 2 hours; cover up where possible
8–10 | Very high | Skin damages quickly | SPF 50, water-resistant 80 min, reapply more often, shade required at midday
11+ | Extreme | Sunburn in minutes | SPF 50, full coverage clothing, hat, sunglasses; avoid outdoor exposure 10am–4pm

This is the EPA's official scale, aligned with WHO global guidance. The reapplication cadence in the right column is from the American Academy of Dermatology.

Why the UV Index is not just a "summer thing"

Two facts that confuse most people:

The UV Index can hit 8 in March or October. It is not strictly a July number. Elevation, latitude, snow reflection, and cloud cover all shift it. A spring ski day at altitude often runs higher UV than a beach day at sea level.

Clouds barely help. Up to 80% of UV penetrates cloud cover according to the World Health Organization. "Overcast" is not a sun protection plan.

For a deeper look at why daily SPF matters even on slow-feeling days, see Is Daily Sunscreen Worth It? Wrinkles, Windows, Answers.

What changes at each level

UV 0–2 (Low)

The risk to most skin types is minimal, but if you are outside more than about an hour the EPA still recommends SPF 30 on exposed skin. People with very fair skin, a personal or family history of skin cancer, or photosensitivity drugs should treat this band the same as Moderate.

UV 3–5 (Moderate)

This is where casual exposure starts to matter. Burn time for unprotected fair skin is roughly 30 to 45 minutes. The EPA's standard advice: stay in shade between 10am and 4pm where reasonable, wear sun-protective clothing, and apply broad-spectrum SPF 30+. If you are running, biking, or hiking, switch to a water-resistant formula.

UV 6–7 (High)

The damage rate roughly doubles relative to Moderate. Reapplication every two hours is no longer a polite suggestion; it is the protection plan. SPF 50 buys margin for thin application. This is the band where most US summer mornings sit, and it is the band where most "I only wore it once" failures happen.

UV 8–10 (Very High)

Burn time on unprotected skin drops to under 15 minutes for fair skin tones. SPF 50, water-resistant 80 min, reapplied immediately after sweating or swimming. Hat and sunglasses are not optional. If you have to be outdoors at midday for a long race, match, or outdoor wedding, treat reapplication as part of the schedule, not a break in it.

UV 11+ (Extreme)

Common at high altitude, in low latitudes, and near reflective surfaces (snow, water, white sand). Sunburn possible in single-digit minutes. The realistic plan is to avoid midday outdoor exposure when possible, and to wear long sleeves plus a wide-brimmed hat plus SPF 50 on every exposed surface when not.

What SPF stick actually works at high UV

The SPF number on the label is tested under conditions that almost no one replicates in real life. The EPA and AAD both note that real-world application is usually thinner and less frequent than the test protocol assumes. At UV 6 and above, this gap matters. Three things stop mattering on a high-UV day and three things start mattering more.

Stops mattering at high UV:

The exact filter class (chemical vs mineral). Both are FDA-permitted and both work if reapplied. The filter question is covered in Mineral vs Chemical Sunscreen: Which Is Actually Better?.

"Sport" branding language. The legal claim is water-resistant (40 or 80 min), and that is what the FDA validates.

A pleasant scent or texture story. None of that survives a 95°F afternoon.

Starts mattering more at high UV:

Format you will actually reapply. Cream that lives in a bag at home is SPF 0. Stick in your pocket is the cadence you can keep.

Finish on your specific skin tone. A visible white cast at UV 7 in a televised setting is one thing; the bigger problem is that people stop reapplying products they don't like seeing.

Dermatologist-tested formulation. Irritated skin at high sweat plus high UV is a recurring summer story.

A 5-second checklist for high-UV days

Check your weather app's UV Index before leaving the house.

If it shows 6 or higher, plan two reapplications, not one.

Pick a stick over a cream for anything you'll do outdoors past 2 hours.

SPF 50, broad spectrum, water-resistant 80 minutes.

Cover hairline, ear tops, back of neck, and lip line. These are the most-missed zones.

Our take on stick formats specifically, for the field sport case, is in Sunscreen for Field Sports: 90 Minutes of Sweat, One Stick.

Where HAESKN fits

We built the HAESKN SPF 50 Sun Stick for the reapplication problem, not the morning step. The morning step is solved. The midday step is where most sun damage sneaks in, and that is the moment a stick wins over cream or spray.

A short comparison of US-market SPF picks across strengths and formats, alphabetized — one per UV-level use case:

Product | SPF | Format | Notable trade-off
Aveeno Protect + Hydrate Face Lotion | 30 | Lotion | Low-UV-day floor; oat-based, derm-recommended for sensitive skin; lotion means slower reapplication
CeraVe Hydrating Mineral Sunscreen Face | 50 | Lotion, mineral | Derm-recommended mass-market mineral; ceramides included; visible cast on deeper tones
HAESKN SPF 50 Sun Stick | 50 | Stick, clear chemical | Built for mid-day reapplication; clear on every tone; dermatologist tested; US manufactured; newer brand (2024) so independent multi-year reviewer data is thinner
Neutrogena Ultra Sheer Dry-Touch | 70+ | Lotion | Extreme-UV-day pick; widely sold and inexpensive; alcohol base can feel drying
Shiseido Clear Stick UV | 50 | Stick, clear chemical | Premium price; single product; being discontinued by Shiseido
Sun Bum Mineral SPF 50 Face Stick | 50 | Stick, mineral | Familiar mass-market sport stick; visible white cast on medium and dark tones

All four meet FDA OTC sunscreen rules. The differentiator at UV 8 is whether you actually reach for it at noon.

FAQ

Where do I check the UV Index?

Most weather apps display it (Apple Weather, Google Weather, AccuWeather). The official US source is the EPA UV Index forecast.

What's a "safe" UV level?

There is no UV level at which UVA exposure stops counting toward long-term skin aging. The Low band (0–2) is the minimum-protection floor; anything above 2 starts adding measurable damage risk for most skin types.

Does cloudy weather drop the UV Index meaningfully?

Not enough to skip sunscreen. Up to 80% of UV penetrates cloud cover. Treat overcast days as moderate UV unless your weather app says otherwise.

Why does the UV Index spike at altitude?

Less atmosphere to filter the radiation. Ski trips, hikes, and mountain races routinely hit UV 8–11 even when air temperature feels cool. Bring SPF 50 stick.

Is SPF 100 better than SPF 50 at high UV?

The diminishing return is real. SPF 50 blocks roughly 98% of UVB; SPF 100 blocks roughly 99%. The bigger lever at high UV is reapplication, not chasing a higher number on the label.

If you want a stick that holds up the way we needed ours to, the HAESKN SPF 50 Sun Stick is $24 and ships from the US.

About the authors. Eugene Kim is co-founder and product lead at HAESKN. He spent nearly two decades at Estée Lauder Companies, most recently as packaging design lead at Clinique, and is an adjunct professor at Pratt Institute. Sherril HwangBo is co-founder and creative director, former design director at LVMH (Moët Hennessy, DFS) and Ralph Lauren. Both are active runners and padel players, and tested HAESKN's stick format across United Airlines NYC Half training cycles, Reserve Padel Miami courts, and weekly On Running Club Miami runs before launch.

Sources

US EPA, "UV Index Scale" — https://www.epa.gov/sunsafety/uv-index-scale-0

US EPA, "UV Index Search" — https://www.epa.gov/sunsafety/uv-index-search

WHO, "Radiation: The Ultraviolet (UV) Index" — https://www.who.int/news-room/questions-and-answers/item/radiation-the-ultraviolet-uv-index

WHO, "Radiation: Sun protection" — https://www.who.int/news-room/questions-and-answers/item/radiation-sun-protection

American Academy of Dermatology, "Sunscreen FAQs" — https://www.aad.org/public/everyday-care/sun-protection/shade-clothing-sunscreen/sunscreen-faqs