The UV your eyes get
isn't the UV on your skin

Why the weather app's UVI can't tell you about your eyes

• The UV dose your skin receives scales roughly with sin h, the sine of the sun's elevation angle h — the higher the sun, the more each patch of skin receives, so it peaks at solar noon. That's exactly what the horizontal UV index in your weather app measures.
• The cornea and ocular surface are a nearly vertical, forward-facing surface, hit by near-horizontal direct sun. This geometry scales roughly with cot h — the lower the sun, the more it shines straight into the eye, so the geometric weight actually rises.
• The two peaks are therefore clearly offset: when the horizontal UVI is highest at noon, your eyes aren't necessarily at their greatest risk — while in the low-sun hours of early morning and late afternoon, the UV load on the ocular surface can be higher.

What UVI·eye does

It shows the UV exposure curve for your eyes across the day at your location, flags the higher-risk morning and evening windows, and turns that into concrete advice on when to wear sunglasses or a wide-brimmed hat.

• Hourly ocular curveComputes the UV load on the ocular surface from the sun's elevation and incidence geometry — not a copy of the horizontal UVI.
• Morning & evening alertsReminds you during the low-sun windows when eye risk rises, instead of only watching noon.
• Protection adviceHow a wide-brimmed hat, sunglasses and which way you face change ocular exposure — turned into actionable guidance.
• Apple Watch & widgetsSee the current window's eye risk at a glance on your watch and home-screen widgets.
• Data from Apple WeatherUV index comes from Apple Weather (WeatherKit). No third-party backend.
• No ads · no trackingNo third-party analytics, no advertising identifiers. Your location is used only on your device.