Check tonight's sunset forecast

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.

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.

Alpenglow runs natively on iPhone, iPad, Mac, Apple Watch, Apple TV, Apple Vision Pro, Android, and TRMNL e-ink displays. The questions below cover how the forecasts are calculated and how accurate they are.

Yes, Alpenglow is free to download and use. The free version shows today's and tomorrow's sunrise and sunset forecasts and includes the core calculators and sun times for any location.

Alpenglow Pro is an optional upgrade that adds forecast notifications, forecasts up to seven days ahead, Forecast Maps, Vantage Point and other premium features. You can subscribe to Pro monthly or annually, or buy a one-time lifetime unlock. Pro also supports Apple's Family Sharing, so a single purchase can be shared with up to five family members at no extra cost.

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 high-resolution data from the ICON weather model to predict sky color intensity up to 7 days in advance.

Low and mid-level clouds with gaps that allow sunlight through tend to produce the most vivid colors, while complete overcast or perfectly clear skies typically result in less dramatic displays. The forecasts are updated periodically throughout the day as new weather model data becomes available, giving you increasingly accurate predictions as the sunrise or sunset approaches.

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.

Golden Hour is the period just after sunrise and just before sunset when the sun is low in the sky (less than about 6 degrees above the horizon). Its light travels through more of the Earth's atmosphere, producing warm, reddish-gold tones and soft, diffused shadows. Also called "Magic Hour", the evening golden hour runs from when the sun is about 6 degrees above the horizon until sunset, and the morning golden hour mirrors it after sunrise.

How long it lasts depends on your latitude and the time of year: roughly 20–30 minutes near the equator, 30–60 minutes at mid-latitudes, and much longer at high latitudes, especially near the solstices. This low-angle light is prized for portraits, landscapes, and architectural photography. 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.

The free version of Alpenglow shows today's and tomorrow's sunrise and sunset forecasts. With Alpenglow Pro, you can view quality forecasts for up to 7 days in the future, which is especially useful for planning photography outings, outdoor events, or trips where you want to catch the best possible light.

Pro also unlocks forecast notifications that alert you when an upcoming sunrise or sunset is predicted to be above your chosen quality threshold, so you can plan ahead with confidence. You can subscribe to Pro monthly or annually, or purchase a one-time lifetime unlock. Alpenglow Pro also supports Apple's Family Sharing, so a single purchase can be shared with up to five family members.

Yes. Forecast Notifications, part of Alpenglow Pro, 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 and Reminders are free: set an alert for a number of minutes before sunrise, sunset or another event, so you have time to get to your viewing spot. You can choose the timing, the quality threshold, and whether you want alerts for sunrise, sunset or both.

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. Learn more about setting up Family Sharing.

The most vivid sunrises and sunsets occur when specific atmospheric conditions align. Mid- and high-level clouds such as altocumulus, altostratus, and cirrus act as a canvas, catching and reflecting the warm light, ideally covering roughly 30–70% of the sky. Just as important is a clear horizon toward the sun, so its light can reach the underside of those clouds: low cloud on the horizon blocks it, and a completely overcast sky leaves little color.

The reds and oranges themselves come from Rayleigh scattering: at sunrise and sunset, sunlight crosses far more atmosphere, and air molecules scatter the shorter blue wavelengths out of the line of sight. Clean, dry air keeps those colors vivid, while haze and high humidity tend to mute them, which is why the clear air after a storm front passes often produces the most spectacular displays. Alpenglow analyzes all these factors together to predict sky quality, rating each sunrise and sunset so you can decide whether it's worth setting that early alarm or heading out for golden hour.

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're offline, but live updates resume only once you reconnect.

Alpenglow is available on a wide range of platforms. On Apple devices, it runs natively on 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.

On Android, Alpenglow is available through the Google Play Store with full forecast and notification features. Alpenglow also supports TRMNL e-ink displays 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 you at-a-glance forecast information without opening the app.