Hey PH 👋 I'm Max, the solo dev behind Healthy Weather. I built this because I was tired of generic "UV index 3" forecasts that tell me nothing about whether my skin is actually making vitamin D right now. The app uses a custom Vitamin D Index (VDI) derived from peer-reviewed research — converting raw UV data into a number that means something for human skin. It factors in solar altitude, ozone absorption, cloud cover, your Fitzpatrick skin type, age, body exposure, and even sunscreen. The new personalized IU tracking feature just went live today. You can start a session, tell the app which body parts are in the sun, and it estimates your real-time IU production based on live conditions. I know the health app space is crowded. The difference here is transparency: every number has a citation. The full science doc is at healthyweather.app/science, no black boxes. Happy to answer any questions. Roast the landing page if you want, I can take it.

Healthy Weather

Vitamin D forecasts that actually know your skin

Vitamin D forecasts that actually know your skin