Rio’s coastal mountains create microclimates — one bay cloudy while the other clears. Southern winter brings a bright galactic core over darker Serra sites west of the metro glow.
Sea-breeze fog can form after warm afternoons even when upper air looks dry.
Brazil · Guanabara · ~22.9°S
Check the live Tonight score for Rio de Janeiro (cloud, dew, transparency, and astronomical dark), then read the hourly cloud timing chart and moonless dark window on this page.
Use the best clear window clock times after astronomical darkness, and prefer moonless hours when deep-sky contrast matters.
This hub shows moonrise, moonset, illumination, and the longest moonless astronomical-dark interval for Rio de Janeiro. Open Dark Sky Window for the full ephemeris card.
ISS passes are spottable near dusk or dawn when the sky is dark and the station is still sunlit. This page lists the next spottable pass when available.
Learn: Is tonight good for stargazing? · How to see the Milky Way