# Aerzeit: When to Open Windows — Beat damp, mold, and pollen > Weather-based window opening advisories for optimal home ventilation. (iPhone/iPad app by Samuel Harrold.) - Source: https://appshunter.io/ios/app/aerzeit-when-to-open-windows/id6787749300 (this page in markdown: same URL + `.md`) - Developer: [Samuel Harrold](https://appshunter.io/developer/6775297361) - Category: Weather, Lifestyle - Price: Free with in-app purchases - Rating: 5.00/5 from 1 App Store ratings - Age rating: 4+ - Requires: iOS 16.4 · 26 MB - Languages: American English - Released: 2026-07-21 - Data updated: 2026-09-03 - Monetization: freemium - User reviews in markdown: https://appshunter.io/ios/app/aerzeit-when-to-open-windows/id6787749300/reviews.md ## What is Aerzeit? Aerzeit watches the next 48 hours and tells you the stretches when the air outside is in the temperature range you chose — so you know when it's worth opening up instead of leaving the system running. When nothing in the next two days is worth it, it says so. Everything else is yours to switch on: rain, humidity, wind, air quality, pollen, UV, sun position, and the hours you'd actually consider opening. Set it once for your climate and your house, wherever in the country you are. WHAT IT DOES Pick the outdoor temperature range you'd be happy to let in. Aerzeit watches the local forecast and tells you when conditions match — once a day, at a time you choose. It can also tell you the moment a window opens, and the moment to close it again. Turn on the filters that matter where you live: rain, humidity, wind, air quality, pollen, UV, and the hours of the day you'd actually consider opening up. Set a shortest and longest opening, so you don't hear about gaps too brief to use or leave one open longer than you meant to. A 48-hour chart shows every condition in one place, so you can see where they agree and where they don't. Tap "Use current location" to set a spot to roughly 1 km precision, or search for a town. A companion Apple Watch app and complication show the same at-a-glance status on your wrist, and keep themselves current even when your phone is elsewhere. A Home Screen widget shows the next open-window period at a glance. Aerzeit runs in 50 languages, picked on the Locations page beside °C/°F. WHAT IT DOESN'T DO Aerzeit doesn't model your home — it reports the outdoor conditions and leaves the judgement to you. Opening, sizing and timing the actual airing is yours. It reports public weather and environmental data (including air quality, pollen and UV) as a comfort tool, not medical advice; if a health condition makes any of those matter for you, follow your clinician's guidance. PRIVATE BY DESIGN - Empty Privacy Manifest. The app calls none of Apple's required-reason APIs. - No language detection. Aerzeit never reads your phone's language setting — that's one of the required-reason APIs it avoids — so you pick from 50 languages in the app instead. - Minimal data. To fetch a forecast, the app sends a roughly 7 km grid cell to a server in the EU — no account, no identifiers, no raw GPS, no history. Your temperature range and all your filter settings stay on your device. The data export (Settings → Export my data) shows exactly what's held — it's all on your phone. - No accounts. No analytics. No tracking. No advertising. No third-party SDKs beyond a small geospatial maths library. MADE INDEPENDENTLY Aerzeit is built and published by Samuel Harrold, based in Indianapolis, Indiana, USA. Terms of Use: https://www.apple.com/legal/internet-services/itunes/dev/stdeula/ ## Key features - Optimal window opening times - Customizable temperature ranges - Rain, humidity, wind filters - Air quality and pollen alerts - 48-hour forecast chart - Apple Watch companion app ## Pricing and in-app purchases Base price: Free. **Subscriptions** | Subscription | Price | Period | | --- | --- | --- | | Aerzeit Premium | $9.99 | per year | ## Frequently asked questions about Aerzeit ### What is Aerzeit? Aerzeit is a weather application designed to inform you about the best times to open your windows for ventilation. It analyzes local forecasts to suggest optimal periods based on your preferred outdoor temperature and various environmental factors. ### Does Aerzeit have ads? No, Aerzeit is ad-free. The app is designed with privacy in mind and does not contain any advertisements or third-party SDKs for tracking. ### How accurate is Aerzeit's forecast? Aerzeit utilizes local 48-hour forecasts to provide its advisories. While it aims for accuracy, it relies on public weather data and does not model your home's specific conditions. ### What environmental factors does Aerzeit consider? Aerzeit considers outdoor temperature, rain, humidity, wind, air quality, and pollen levels. You can customize which of these filters are most important for your ventilation decisions. ### Can I use Aerzeit on my Apple Watch? Yes, Aerzeit offers a companion Apple Watch app and complication. This allows you to view the same at-a-glance status on your wrist, even when your phone is not nearby. ### Is Aerzeit free to use? Aerzeit is free to download and use with its core features. There is an optional 'Aerzeit Premium' subscription available for $9.99 per year for enhanced functionality. ### How often is Aerzeit updated? The app was last updated on August 8, 2026, with version 0.10.3. Regular updates ensure the app remains functional and incorporates any necessary improvements. ### Is Aerzeit suitable for children? Aerzeit has an age rating of 4+, making it suitable for younger users. The app provides weather information and does not contain any inappropriate content. ## Version history (last 5 releases) ### 0.14.1 — 2026-09-03 Wind and air-quality level names in the forecast chart now match each country's published weather terminology. Corrected in Greek, Finnish, Czech, Croatian, French and Spanish — several were one step off the official scale. ### 0.14.0 — 2026-08-31 Corrections to some level names in several languages. ### 0.13.1 — 2026-08-29 The precipitation filter's lower limit now affects your windows. Its control and the value it saved had shipped months ago while the window calculation never read either, so the description promised a range the app was not applying. If you had set a minimum, you will see fewer windows than before — that is the setting finally doing what it said. The temperature row of the forecast chart now labels every gridline, including the topmost. A mild day could previously show only two numbers and leave the warmest part of the plot unlabelled. A filter's selection band could open with no width when restoring a value saved earlier, and the same fault could interrupt VoiceOver and Voice Control when stepping a value down. Both are fixed. ### 0.11.0 — 2026-08-14 City search now finds a city by its local name as well as its English one, and by any word in the name. A newly added location no longer shows weather for the wrong place before you've chosen one, and on the forecast chart, the duration labels of two short windows that fall close together no longer overlap each other. Rain chance and UV are now correct in Europe. Where a measurement is missing, those rows now show the same question-mark marker the chart already uses elsewhere, instead of the maximum. A strong wind is no longer mistaken for a missing reading, so your wind limit is respected. ### 0.10.3 — 2026-08-08 Apple Watch. Aerzeit now has a companion Watch app and a complication showing your window status at a glance — and it fetches its own forecast, so it stays current even when your phone is elsewhere. The Home Screen widget now comes in medium and large as well as small. The forecast chart reads more clearly: dashed coral means one thing only — a limit you set — and the legend now says so. The recommended-window band shows the whole window, including the part already elapsed. A notification for a window already open now leads with what doesn't go stale: "Open now — close at 4 PM." Fixed: a time range not starting on the hour found no windows at all ("only between 10:03 and 10:27" reported nothing); a "Max open" limit could produce a window far longer than the limit, or no advice at all for the rest of the day; changing a setting moved the chart but left notifications on the old schedule; the widget and Watch could disagree with the phone; Settings could crash on open. Also: a "Leave a Review" link on the About page, your primary location marked in the list, and a correction — the grid cell the app sends is about 7 km across, not the 3 km we previously stated. --- *Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-09-03.*