UV Index Today
Real-time solar radiation monitoring
Blog
One mechanism or one event per piece, with numbers you can check. FAQ-style answers live in the Guide. Who writes this: About.
Sep 11, 2026
Ten to Four Is Not a Global Clock
EPA clocks the strongest UV at 10 a.m.–4 p.m. That six-hour block is mid-latitude summer shorthand. WHO’s protect-at-3 line opens earlier, runs later, or never opens—depending on latitude, season, and whether the wall clock matches solar noon.
Sep 7, 2026
Skin Type Changes Burn Minutes, Not the Index
The live UV index is a sky rate shared by everyone under it. Fitzpatrick type changes how fast that rate can redden unprotected skin—not whether the number applies.
Sep 5, 2026
The Bottle SPF Assumes a Coat You Rarely Put On
Lab SPF is scored at 2 mg per square centimetre. Typical use is often 0.5–1.5 mg, so the number on the bottle is not the protection on the skin.
Sep 3, 2026
Polarized Is Not a UV Rating
Polarization knocks down glare from water and road. It does not, by itself, stop UV. The label that matters is UV400 or 100% UVA/UVB—plus a wrap that closes the sides.
Aug 30, 2026
Nepal–Tibet Glacier Collapse Sends a Wall of Water Down the Trishuli
Dated recap of the 26 August 2026 ice-rock avalanche on the Nepal–Tibet border, with links to primary reporting—and why a monsoon break at altitude is still a UV day.
Aug 26, 2026
The Burn Shows Up After You Leave
UV does its damage while you still feel fine. Labs score sunburn 16–24 hours later—feeling unburned on the outing is not an all-clear.
Aug 25, 2026
Kyushu Heads for 40°C Today as Heat Stroke Alerts Cover 41 Prefectures
MoE and JMA have Heat Stroke Alerts in 41 prefectures on Tuesday—Kumamoto, Kurume, and Hita near 40°C—plus why a WBGT alert is not a UV all-clear under late-August sun.
Aug 22, 2026
Same Latitude Is Not the Same UV
Southern-hemisphere summer sits closer to the sun, under thinner ozone and cleaner air. Peak UV at matching southern latitudes can run about 40% higher than in the north—do not pack northern habits south.
Aug 21, 2026
Hours at UV 4 Can Outdose Minutes at UV 8
The UV index is a rate, not a daily budget. Three hours at a steady 4 can deliver more erythemally weighted dose than twenty minutes at 8—plan the length of the outing, not only the peak.
Aug 19, 2026
A Shadow Shorter Than You Means High UV
If your shadow is shorter than you are, the sun is above 45° and UV is already in a high band. WHO’s protect-at-3 line often arrives earlier, while the shadow is still longer than you.
Aug 17, 2026
UAE Inland Hits 49°C Today as Clouds Build in the East
NCM has inland highs of 44–49°C on Monday—Liwa near 48°C, Al Ain near 47°C, Dubai 43°C—plus why the midday outdoor-work break does not cancel solar-noon UV.
Aug 15, 2026
Broken Clouds Can Raise UV Above a Clear Sky
When the sun still throws a shadow, nearby clouds can bounce extra UV down—often about 20–30% above the clear-sky number. Puffy weather is not cover.
Aug 13, 2026
A Baseball Cap Leaves the Ears and Neck
A cap shades the crown and forehead. Ears, cheeks, and the back of the neck sit almost in open sun—brim width and a neck flap change the dose, not the fact that you put something on your head.
Aug 11, 2026
Europe’s Fifth Heat Wave Hits the UK, France, and Spain This Week
Midweek highs near 36°C in England, approaching 40°C in southeastern France, and about 42°C in Córdoba—plus why heat alerts still leave midday UV unchecked.
Aug 9, 2026
A Cotton T-Shirt Barely Blocks UV
Everyday tees often sit near UPF 7 dry and about UPF 3 when wet. Clothes cover skin—but weave, color, stretch, and wetness decide how much UV still gets through.
Aug 7, 2026
UV Still Hits You Underwater
Cool water hides the burn. About 40% of UV still reaches ~50 cm depth; in very clear water a high index can persist meters down—treat a swim like open-sky time, not shelter.
Aug 5, 2026
Higher Elevation Means Stronger UV—Even When the Air Feels Cool
UV rises with altitude as the atmosphere thins. Cool mountain air is not a low-UV signal—use elevation, snow, and today’s peak when you plan a hike or ski day.
Aug 3, 2026
UV Peaks Before the Day Feels Hottest
Solar noon drives the day’s highest UV. Air temperature often peaks hours later—so a cool late morning can still sit under a High or Extreme index.
Jul 31, 2026
Shade Cuts Direct Sun. It Does Not Cancel UV.
Why beach umbrellas, tree cover, and patio shade still leave you exposed—and how reflection from sand, water, and snow changes the dose.
Jul 30, 2026
Phoenix Faces 116°F This Weekend as Heat Dome Hits the Desert Southwest
Breaking weather update for July 31–August 2, 2026—Phoenix may tie 116°F records under an Extreme Heat Warning, while South Florida forecasts Extreme UV near 12.
Jul 28, 2026
How to Use a Live UV Index Before You Go Outside
The three numbers on UV Index Today—current, today’s peak, and the next few hours—and how to match them to shade, clothing, and sunscreen.