About Sunsethue
On a winter evening in February 2022, I was treated to an amazingly colourful and vivid sunset. I thought: wouldn’t it be cool if it would be possible to forecast how beautiful a sunset is expected to be. That night, the idea of Sunsethue was born. A couple weeks later, the first version of Sunsethue was born, albeit with quite inaccurate forecasts.
Before continuing, I should probably introduce myself. My name is Maarten, and I’m a computer science student from Belgium with a passion for meteorology. I’m developing Sunsethue in my free time, and this project is a match made in heaven for me, because it encompasses both computer science and meteorology.
The story of Sunsethue
Sunsethue has been constantly in development since its inception in February 2022. I invested a lot of time in constantly checking forecasts and improving the underlying model to make these forecasts. On the other hand, the website went from a single-page web app to a full website. New information and functionalities are regularly added to the Sunsethue model and the web app.
In November 2023 Sunsethue Alerts was launched after a user suggested a notification feature. It became a great success, with over 100,000 alerts having been sent out to over 2,000 users worldwide. The premium version of alerts brings in the necessary funds to operate the website and run the sunset forecast model.
Despite all my best efforts to make the model as perfect as possible, I was getting limited by the overall structure of the model. The model which was in use until November 2024 only accounted for clouds straight above a certain location. To combat these issues, I used my summer holiday break of 2024 to come with a whole new way of quality prediction.
Ray-based model
This new way of making predictions is more complex, but the main thing is that it accounts for all clouds that may affect the sunrise or sunset, even if they are far away. To explain it in simple terms: rays are cast in the direction of sunset, based on the cloud cover along the ray, a quality metric is computed. A cloud which is situated over 400km (250mi) can block the sun at sunset, and that is now accounted for.
In the summer of 2025 I took some time to restructure the underlying code to make it easier to add different metrics, like for example the highlight time metric. With this restructuring, you are now also able to check the composite sunrise and sunset forecast maps for Europe, North America and Australia without having to scroll through different timesteps.
After in-depth testing by comparing the predictions to actual sunsets (on webcams), it became clear that this new method is greatly outperforming the previous way of forecasting. In the autumn of 2024, this new model got introduced together with a complete redesign of the web app.
READ MOREStructure of Sunsethue
I decided to build Sunsethue in multiple components: the Sunsethue model, the API and the website. Two times a day, the model runs using data from the german ICON weather model, and calculates the metrics for all locations worldwide. These forecasts can then be accessed using the API. The web app uses this API to display the forecasts in a user-friendly way.
Besides that, I decided to keep the website and API separate, so that other people and services can access the API as well. The API is documented and can be used for free in your own projects. In the future, there will also be a paid commercial plan, so that (hopefully) you will be able to access Sunsethue’s forecasts through other apps and websites as well.
SUNSETHUE APIMission
Sunsethue exists for anyone who wants to know if the sunrise or sunset will be worth it. For people who like to wonder at the spectacle or professional photographers who need the best light to capture the most amazing pictures.
A beautiful sunrise or sunset is something positive, something that can inspire and bring people together. Besides serving people who are actively searching for a sunrise or sunset forecast, I also want to reach people who might never go outside to attend the spectacle. I hope Sunsethue may help spread the power of a vivid sunrise or sunset to more people, by providing forecasts where anyone can rely on.
Future visions
The main focus is to continue improving the core service of Sunsethue: the sunset forecasts. I plan to do this by adding the ability to rate past sunrises and sunsets, to pinpoint the weaknesses in the model. Besides this, I also want to make historical forecasts available through the web app. I already experimented with running the model on historical data, to make long-term average maps to see where and when the best sunsets tend to occur. I plan on making this data available through some blog posts on the matter, or an interactive explorer.
In the long-term, I would like to introduce more information regarding sunrises and sunsets (besides the cloud cover and general quality metric). I’m already experimenting with a highlight time metric. Some other ideas include the forecasted duration of the sunset and the colour of the sunset. There is also a lot of improvement possible by upgrading the number of model runs, the resolution and forecasts for more than three days ahead. Due to computational limitations and uncertainty in the weather model forecasts which Sunsethue relies on, these things cannot be implemented at this time.
Supporting Sunsethue
Sunsethue started out as a small side project, but has grown to a sizable project. I’ve put a lot of time into it, and I’m proud of what it has become already. Still, there are a lot of improvements to be made. Sunsethue is already attracting sunset lovers worldwide, but there are many that are being left in the dark about potentially beautiful upcoming sunsets. The best way to support Sunsethue is to share the word about Sunsethue. Besides this, feedback also helps me a lot, so if you have any feedback or ideas, let me know!
GIVE FEEDBACK© 2026 - Sunsethue (v0.10.2-beta)
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