Rio de Janeiro residents and tourists were baking Monday in scorching temperatures as the city's crowded pre-Carnival street parties swung into full gear.

A heatwave is hitting several parts of Brazil, with temperatures of between 40 and 44 degrees Celsius (104 and 111 degrees Fahrenheit) expected to last for three days in a row.

A sizzling weekend in Rio saw residents crowd beaches while a leading samba school canceled its parade rehearsal on Copacabana beach.

Meanwhile, some of the world's top tennis stars will face the heat on and off the court this week at the Rio Open.

The city said it had reached a level four heat alert -- with five being the maximum.

In response, it has opened up dozens of cooling and hydration points.

In Copacabana, wilting doorman Robson Oliveira stopped to take a picture of an electronic display showing the temperature at 39C.

"This heat is unbearable," he told AFP.

"I'm not used to it. It's about time for a little rain to cool off."

Rio Mayor Eduardo Paes said Sunday that the city would not cancel events due to extreme temperatures during Carnival, which attracts millions of tourists and is a major earner for the city.

"But it is obvious that we can call the attention of (Carnival) revelers to say: 'Hey, drink more water, hydrate yourself better, take certain precautions,'" he said.

"No one is going to suspend any activity in the city, even in an extreme event."

Raquel Franco, chief meteorologist of the Rio Alert System said the current heat record for February in the city was 41.8C, recorded in February 2023.

A maximum of 42C was forecast for Monday.

With no rain on the horizon, "we may have one of the driest Februarys in history," Franco said.

Rio de Janeiro's health secretary Daniel Soranz said the city had already seen in recent weeks "an increase in people seeking emergency care with problems related to the heat, mainly dehydration and a worsening of chronic diseases."

It was even harder to find respite from the heat in the city's favelas -- treeless urban heat islands of brick and concrete that often suffer the worst of heatwaves.

In the Bateau Mouche favela in western Rio, residents doused themselves in water to cool down on Sunday, and an AFP reporter saw an elderly man faint due to high temperatures.