Soaring temperatures in Rio de Janeiro set off the fire sprinklers Friday in a downtown shopping mall as the thermometer topped 40 degrees Celsius (102 degrees Fahrenheit).

In the sunshine, temperatures rose to 50 degrees Celsius, leaving residents of the metropolis gasping.

But customers taking refuge indoors at Shopping Leblon gained unexpected relief when the sprinklers came on.

"Owing to the high temperature registered in the city we had the sprinklers come on automatically. Things got back to normal in 20 minutes and the mall has been cleaned up," the center said on its Twitter feed.

Brazil's Meteorological Office recorded temperatures soaring from a low of 24 degrees Celsius to beyond 40 at some points of the city, sending residents and New Year tourists alike streaming to the beaches to seek respite in the sea.

The sticky conditions proved too much for the air conditioning systems at Rio's Galeao international airport and Santos Dumont domestic airport, leaving commuters baking in indoor temperatures topping 30 degrees Celsius, Globo television reported.