A worldwide hourly forecast for rainbow conditions.
Open Bowcast · Live map · Worldwide Now · City forecasts · Science
Bowcast estimates when and where sunlit rain may align for a rainbow. It reads about 40 weather forecast members through the geometry of rainbow formation, then shows the estimated chance, best hour and direction to face.
- A worldwide map for any searched or geolocated position.
- A current-hour ranking of cities where rainbow conditions align now.
- Seven-day hourly city forecasts with the most promising viewing window.
- Practical viewing direction based on solar geometry.
- Optional alerts and anonymous sighting outcomes.
- An installable progressive web app plus iOS and Android applications in preparation.
Bowcast keeps the forecast estimate separate from observation and geometry:
- Estimated chance is weighted agreement across about 40 forecast members. It is not yet calibrated as an observed occurrence frequency.
- Observed ingredients describe recent sunlight and rain evidence. They do not confirm that a rainbow is visible.
- Viewing guidance explains when and where to look. It does not increase the occurrence estimate.
The forecast combines published atmospheric-optics relationships with tunable operational heuristics. Read the full explanation on the Bowcast science page.
Bowcast requires no account and uses no advertising trackers. Optional sighting reports are anonymous and use coarse location data.
Bowcast is in active production preparation. This public repository is the project page for discovery, launch updates and feedback. The application source is maintained privately.
Questions or feedback can be shared through GitHub Issues.