Frequently Asked Questions

Your Vitamin D₃ window is open when conditions are actually producing Vitamin D. The index combines UV strength with the sun’s angle so it reflects the UVB reaching the ground, not just overall UV:

• 0: No Vitamin D₃ is produced.
• 0–1: Very negligible — only a tiny amount, if any.
• 1 and above: Window open — the higher the number, the faster your body synthesizes it.

For the full calculation, see how the Vitamin D₃ Index is calculated.

The standard UV Index is weighted toward UVA and sunburn risk, so at low sun angles it can look promising while the atmosphere still blocks the UVB you need for Vitamin D. See how the Vitamin D₃ Index corrects for this.

Our Vitamin D₃ Index and health metrics are our own calculations; weather and UV data are powered by  Weather, fetched directly on your device. More on our data sources.

Different weather apps use different data sources and weather models. A small difference in temperature (around 1°C) or humidity is completely normal and expected. Neither is wrong — they just use different methods and accuracy levels to calculate the weather at your location.

We continuously refine and expand our data sources in the background to keep your weather data as accurate as possible.

Healthy Weather is an iOS app built around how weather and sunlight affect wellbeing. It layers health-related weather insight — especially our Vitamin D₃ Index for Vitamin D timing and sun safety — alongside everyday conditions so you can plan with context, not just temperature and icons.

Healthy Weather is a premium, ad-free tool designed to give you useful health-related weather information without tracking or selling your information. You get your first 2 weeks completely free to explore the Vitamin D₃ Index, interactive charts, and personal vitamin D₃ tracking. After that, a subscription is required for full access. Without a subscription, only a limited part of the app is available for free.

Healthy Weather works in all regions worldwide. Weather, UV, and Vitamin D₃ Index data are available globally. The app uses your device location to show local, health-focused forecasts.

No. We currently only support device location — there is no manual location input.

No. Healthy Weather is a planning tool — not a medical device. All data, including Vitamin D₃ windows and UV forecasts, is for general information only. It can help you make better decisions, but it is not a substitute for professional medical advice or your own judgment.

You are ultimately responsible for how you act on the information. The app cannot account for your personal health situation, skin type, medications, or local conditions, and data may occasionally be inaccurate due to technical bugs or third-party outages. Always consult a doctor if you have concerns about sun exposure or any health condition.

The developer is not liable for any health issues resulting from the use of this app. For the full legal terms, see our Terms of Use.

We understand that a single app might not give you all the weather data you want, so Healthy Weather makes it simple to jump to another app with one tap.

A few popular apps are already listed in Settings for convenience. If the app you want isn’t listed, you can enter any custom URL in Settings. Two types of links work:

• Universal Links look like a regular website URL (e.g. https://example.com). If the app is installed, iOS opens it directly. If not, it opens the website in Safari as a fallback. Not every app supports Universal Links — it’s up to each app’s developer to enable them.
• URL Schemes are custom app addresses like appname://. These open the app directly but have no web fallback — nothing happens if the app is not installed. Most apps support this.

To find the right link for an app: search online for “[App Name] iOS URL scheme”, or check the app’s own website or developer documentation. Not sure? Contact us and we’ll help you find the right link.

The linked app must be installed for URL scheme links to work. All trademarks belong to their respective owners. Healthy Weather is not affiliated with any third-party apps.

We have no plans for Android unless there is significant demand.

Use the links in the app under Settings → Feedback (e.g. Report a Bug, Request a Feature, Contact the Developer). You can also reach us via the Support page on our website. We read all messages and use them to improve Healthy Weather.

On your iPhone, locally. Healthy Weather doesn’t upload your sessions to a server.

If you delete and reinstall the app, your history is gone. iOS wipes all on-device app data when you uninstall, so reinstalling starts you fresh.

Your history doesn’t sync to your iPad or other devices yet — each device keeps its own history. iCloud sync is planned for a future update.

Not in this version. Export, backup, and deleting individual sessions are planned for a later update.