Rio de Janeiro

The sea in Rio de Janeiro peaks in January, when the water averages around 28°C.

The main swimming season runs from January – December, when surface temperatures stay comfortable for extended sessions.

On average, 12 months a year sit above 20°C — the threshold most swimmers describe as pleasant without a wetsuit.

The coldest month is typically July at around 24°C, when cold-water swimmers dominate the coast.

Rio de Janeiro sits in the Southern Hemisphere, so the warmest sea coincides with the December–February summer and the coolest with July–August.

Long-term climatology for Rio de Janeiro shows an annual mean sea temperature of 26°C, ranging from 24°C in winter to 28°C at the summer peak.

The seasonal swing is roughly 4°C between the coldest and warmest month — a useful yardstick when comparing years or checking whether the current sea is running above or below average.

Recent decades have trended slightly warmer at Rio de Janeiro, in line with regional sea-surface temperature records for the wider basin.

Monthly averages below are drawn from multi-decadal climatology and are updated as new observations arrive.