How Alpenglow Predicts Sunsets & Sunrises

Alpenglow's forecasts are generated by its own model, which analyses cloud cover, moisture and pressure across multiple altitudes to score how colorful each sunrise and sunset is likely to be — up to 7 days in advance.

By Andrew Yates·Building Alpenglow since 2016

The weather data behind it

Alpenglow's model uses high-resolution data from theICON weather model, produced by Deutscher Wetterdienst (DWD), Germany's national meteorological service. Forecasts are updated periodically throughout the day as new weather model data becomes available, so predictions become increasingly accurate as the sunrise or sunset approaches.

For nearly its entire ten-year history, Alpenglow's forecasts were powered by SunsetWX, a service built on the NAM and GFS weather models. The in-house model went live in early 2026 — thefull story is on the blog — and owning it end-to-end is what unlocked Forecast Maps, the 7-day forecast horizon, and many of the features that shipped with the 10-year update.

What the model analyses

Cloud cover at multiple altitudes

Low and mid-level clouds with gaps that let sunlight through tend to produce the most vivid colors. Completely overcast or perfectly clear skies typically result in less dramatic displays.

Humidity and moisture

Moisture in the atmosphere scatters shorter blue wavelengths of light, letting reds, oranges, and pinks dominate the sky at sunrise and sunset.

Pressure systems

Barometric pressure shapes how weather systems move and clear. Clean air after a storm front passes often produces the most spectacular displays.

Aerosols and air quality

Aerosol concentration affects how light scatters near the horizon — a factor in both the intensity and the reach of sunset color.

How accuracy improves over time

Forecast accuracy depends primarily on the underlying weather 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 because localized patterns aren't always captured by broader weather models.

Around each sunrise and sunset, Alpenglow users can submit Field Reports — real-time observations of what the sky actually looked like. These crowd-sourced reports are compared against the forecast and used to refine future predictions. And because the model is updated as fresh weather data arrives, the closer you are to the event, the more accurate the forecast becomes.

Frequently asked questions

Which weather model does Alpenglow use?▼

Alpenglow's forecasts are generated by its own model, which uses high-resolution data from the ICON weather model produced by Deutscher Wetterdienst (DWD), Germany's national meteorological service. Alpenglow analyses that data — cloud cover at multiple altitudes, moisture, and pressure — to score how colorful each sunrise and sunset is likely to be.

How far ahead can Alpenglow forecast a sunset?▼

Forecasts extend up to 7 days ahead, and are updated periodically throughout the day as new weather model data becomes available. The free app shows today’s forecast; Alpenglow Pro unlocks the full 7-day horizon and quality-threshold notifications.

How accurate are the forecasts?▼

Accuracy depends primarily on how reliable the underlying weather forecast is for your location. In regions with dependable weather forecasts, quality predictions are highly accurate; coastal and mountainous areas are harder because localized patterns can escape broader models. Forecasts get more accurate as the event approaches, and user-submitted Field Reports of actual sky conditions are used to refine future predictions.