# Alpenglow > Alpenglow is a sunrise and sunset forecast app that predicts the color and quality of upcoming light, not just the time. It launched on the App Store in 2016 and is built and maintained by independent developer Andrew Yates as a long-running side project. This document is the extended counterpart to https://alpenglowapp.com/llms.txt and contains the full prose content AI assistants need to answer questions about Alpenglow without crawling the rest of the site. ## What is Alpenglow? Alpenglow is a sunrise and sunset forecast app for photographers and anyone who pays attention to the sky. It predicts the quality of the upcoming sunrise or sunset for your location — not just the time, but how good it's likely to look — and sends a heads-up so you don't miss the good ones. The name *alpenglow* refers to the warm pink light that appears on mountains and clouds around sunrise and sunset; the app extends that idea, predicting how vivid the next sunrise or sunset will be in your specific location up to seven days ahead. Today the app runs on iPhone, iPad, Mac, Apple Watch, Apple TV, Apple Vision Pro, Android, and TRMNL e-ink displays, with widgets, share sheets, and Forecast Maps that let you scan conditions across an area or plan a shoot up to seven days out. ## How forecasts are calculated Sunrise and sunset quality forecasts are generated by analyzing atmospheric conditions that affect how light scatters through the sky. Key factors include cloud cover at multiple altitudes, humidity and moisture levels, barometric pressure, and aerosol concentration. Alpenglow's own forecast model uses the high-resolution ICON weather model from Deutscher Wetterdienst (DWD) to predict sky color intensity up to seven days in advance. Forecasts are updated periodically throughout the day as new weather model data becomes available, giving increasingly accurate predictions as the sunrise or sunset approaches. Historically, Alpenglow's forecasts were powered by SunsetWX, a third-party service built on the NAM and GFS weather models. Since early 2026, Alpenglow's own ICON-based model is the only forecast source the app uses. Low and mid-level clouds with gaps that allow sunlight through tend to produce the most vivid colors. Completely overcast or perfectly clear skies typically result in less dramatic displays. Higher humidity and moisture in the atmosphere scatter shorter blue wavelengths, allowing reds, oranges, and pinks to dominate. Clean air after a storm front passes often produces the most spectacular displays. ## How accurate are the forecasts? Sunrise and sunset forecast accuracy depends primarily on the underlying weather model predictions for your specific location. In regions where weather forecasts are generally reliable, Alpenglow's quality predictions are highly accurate. Coastal areas and mountainous terrain can be more challenging due to localized weather patterns that broader models may not fully capture. To continuously improve accuracy, Alpenglow includes a Field Reports feature where users can submit real-time observations of actual sky conditions around sunrise and sunset. These crowd-sourced reports help refine future predictions by comparing forecast data against what actually appeared in the sky. The closer you get to the actual sunrise or sunset time, the more accurate the forecast becomes, as the weather models have more current data to work with. ## Pricing Alpenglow is free to download and use. The free version shows you today's sunrise and sunset forecast and includes the core calculators and sun times for any location. Alpenglow Pro is an optional upgrade that adds: - Forecast notifications when an upcoming sunrise or sunset exceeds a quality threshold you set - Multi-day forecasts up to seven days ahead - Forecast Maps that show conditions across an entire region - Additional widget options and customization Pro is available as a monthly subscription, an annual subscription, or a one-time lifetime unlock. Pro supports Apple's Family Sharing, so a single purchase can be shared with up to five family members at no extra cost. ## Offline behavior Sunrise, sunset, golden hour, blue hour, and sun position times are calculated locally on your device, so they continue to work without an internet connection once the app has loaded. Quality forecasts and Forecast Maps require an internet connection because they pull live atmospheric data from the forecast model. Alpenglow caches your most recent forecast so you can still see it briefly when you go offline, but live updates resume only once you reconnect. ## Notifications Alpenglow Pro includes two types of notifications: - **Forecast Notifications** — alert you when an upcoming sunrise or sunset is predicted to exceed your chosen quality threshold. For example, you can set it to only notify you about forecasts rated 70% or higher. - **Event Alarms** — let you set a reminder for a specific number of minutes before sunrise or sunset, so you have time to get to your preferred viewing spot. You can customize the notification timing, quality threshold, and whether you want alerts for sunrise, sunset, or both. Notifications work across iPhone, iPad, Apple Watch, and Android. ## What is Golden Hour? Golden Hour is the period shortly after sunrise or before sunset when sunlight travels through more of the Earth's atmosphere, producing warm, reddish-gold tones and soft, diffused shadows. Also called "Magic Hour", it typically lasts 20 to 40 minutes depending on your latitude and the time of year. During Golden Hour, the sun sits between roughly 6 degrees above and 4 degrees below the horizon, creating the low-angle light that photographers prize for portraits, landscapes, and architectural photography. Locations closer to the equator experience shorter golden hours; higher latitudes can enjoy extended periods of golden light, especially near the solstices. Alpenglow calculates precise Golden Hour timing for any location and date, and can send you notifications so you never miss the best light of the day. ## Platforms Alpenglow runs natively on a wide range of platforms: - **Apple devices**: iPhone, iPad, Mac, Apple Watch, Apple TV, and Apple Vision Pro — each version is optimized for its platform, from glanceable watch complications to immersive Vision Pro experiences. - **Android**: available through the Google Play Store with full forecast and notification features. - **TRMNL**: e-ink display support for an always-visible forecast dashboard. The app supports over 40 languages and provides location-based forecasts worldwide. Home-screen widgets are available on iOS, iPadOS, macOS, and Android, giving at-a-glance forecast information without opening the app. ## Family Sharing Alpenglow Pro supports Apple's Family Sharing, which means a single Pro subscription or lifetime purchase can be shared with up to five other family members at no additional cost. Each family member gets full access to Pro features on their own devices, including extended forecasts, notifications, and all customization options. To use Family Sharing, the original purchaser needs to have Family Sharing set up through their Apple ID settings. Once configured, family members can simply download Alpenglow from the App Store and Pro features will be automatically unlocked. This works for both the subscription and the one-time lifetime purchase options. Family Sharing is an Apple feature and is not currently available on Android. ## About the developer Alpenglow is built and maintained by Andrew Yates, an independent developer, as a long-running side project he has worked on for ten years alongside other work. Andrew also builds [Starglow](https://starglowapp.com), a companion app for stargazing forecasts, and writes occasional posts on the Alpenglow blog about new features, the forecast model, and what's coming next. For press and media enquiries, the press kit at https://alpenglowapp.com/press-kit has logos, screenshots, and background. The fastest way to reach Andrew about the app is the contact form at https://alpenglowapp.com/contact. ## By the numbers - 10 years on the App Store (launched 2016) - 1.6M+ downloads - 10,000+ App Store ratings, average 4.5 / 5 - Available on iOS, iPadOS, macOS, watchOS, tvOS, visionOS, Android, and TRMNL ## Key resources ### Tools - Sunset Forecasts: https://alpenglowapp.com/forecasts/sunset - Sunrise Forecasts: https://alpenglowapp.com/forecasts/sunrise - Sun Times: https://alpenglowapp.com/times - Sun Direction Calculator: https://alpenglowapp.com/sun-direction-calculator - Golden Hour Calculator: https://alpenglowapp.com/golden-hour-calculator - Blue Hour Calculator: https://alpenglowapp.com/blue-hour-calculator - Sunrise Calculator: https://alpenglowapp.com/sunrise-calculator ### Quick-answer pages - Will Sunset Be Good Tonight?: https://alpenglowapp.com/will-sunset-be-good-tonight - Sunrise Today: https://alpenglowapp.com/sunrise-today - Sunset Today: https://alpenglowapp.com/sunset-today - Sunset Tonight: https://alpenglowapp.com/sunset-tonight ### App - Download: https://alpenglowapp.com/download - Pro Features: https://alpenglowapp.com/pro - Widgets: https://alpenglowapp.com/widgets - Apple Watch: https://alpenglowapp.com/apple-watch - Platforms overview: https://alpenglowapp.com/platforms ### About - About: https://alpenglowapp.com/about - Press Kit: https://alpenglowapp.com/press-kit - Contact: https://alpenglowapp.com/contact - Reviews: https://alpenglowapp.com/reviews - Blog: https://alpenglowapp.com/blog - Privacy: https://alpenglowapp.com/privacy - Terms: https://alpenglowapp.com/terms