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
Tonight is 22 Oct, times in America/Sao_Paulo (GMT-3), computed with astronomy-engine for 22.91° S, 43.17° W. Climate: NASA POWER monthly means, 2001-2020, cloud and rain averaged over the whole day.
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.
Tonight (22 Oct) the moonless dark window in Rio de Janeiro runs from 3:16 AM to 3:56 AM (GMT-3). This hub also shows moonrise, moonset and illumination; open Dark Sky Window for the full ephemeris card.
Tonight (22 Oct) astronomical darkness in Rio de Janeiro runs from 7:18 PM to 3:56 AM (GMT-3). This hub lists sunset, civil, nautical and astronomical dusk and the matching dawn times, plus when the Moon and planets are highest. Astronomical darkness starts when the Sun is 18° below the horizon.
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.