Celestial Atlas › Learn › Weather and cloud cover for any date: forecast, history and climatology
Weather and cloud cover for any date: forecast, history and climatology
Seeing an eclipse depends on clouds. Celestial Atlas shows the real forecast for future dates within about two weeks, real historical weather (ERA5 reanalysis) for dates since 1940, and — for everything else — a clearly labelled climatology (average conditions for that date and hour). It never invents weather.
Which data you get for which date
| Date you pick | What the weather card shows |
|---|---|
| Before 1940 | “No weather data” — instrumental reanalysis does not exist. |
| 1940 to a few days ago | Historical reanalysis for that exact hour (temperature, wind, pressure, humidity, cloud layers, visibility). |
| Now to ~2 weeks ahead | Forecast. |
| Further ahead | “No forecast available” plus climatology: typical temperature, mean cloud cover and chance of rain from past years. |
Clouds on the globe
When enabled, Earth's cloud layer is replaced by a global grid of cloud cover from Open-Meteo for the selected hour, so the cloud pattern over your marker matches what the satellite-assimilated analysis says for that time. A cached grid is reused to keep the app fast and gentle on the free API. The card also reports the sky-clarity rating (cloud cover, visibility and precipitation combined) and the cloud forecast for the moment of an upcoming eclipse at your place.
Why we label climatology
Weather cannot be forecast beyond about two weeks. Rather than show something that looks like a forecast, the atlas shows what is statistically typical and says so in the card. If the weather service is unreachable the card says “unavailable” and everything else keeps working.
What is real and what is illustrative
- Real Forecast and reanalysis values; the cloud grid for the picked hour.
- Illustrative The globe's cloud rendering resolution (20° grid blended with a detailed texture) and the colour of storms.
Frequently asked questions
Can I check the weather on a past eclipse day?
Yes for dates since 1940: pick the eclipse date and your place; the card shows the reanalysis for that hour, including the cloud cover at maximum.
Why does it say climatology for next year?
No forecast exists that far ahead, so the atlas shows typical conditions for that date and hour from past years and labels them as an average, not a prediction.
Where does the weather come from?
From Open-Meteo, which serves the ERA5 reanalysis, national forecast models and a free geocoding service, under a CC BY 4.0 licence.