Rescuers rushed to evacuate people stranded by devastating floods across the southern Brazilian state of Rio Grande do Sul on Tuesday, with at least 90 dead, thousands left homeless, and desperate survivors seeking food and basic supplies.

On the outskirts of Eldorado do Sul, 17 kilometres (10.5 miles) from the state capital of Porto Alegre, many people were sleeping on the roadside and told Reuters they were going hungry. Entire families were leaving on foot, carrying belongings in backpacks and shopping carts.

“We’ve been without food for three days and we’ve only just got this blanket. I’m with people I don’t even know, I don’t know where my family is,” said a young man who gave his name as Ricardo Junior.

The flooding has hampered rescue efforts, with dozens of people still waiting to be evacuated by boat or helicopter from stricken homes. Small boats crisscrossed the flooded town searching for survivors.

The state’s Civil Defense agency said the death toll had risen to 90 with another four deaths being investigated, while 131 people were still unaccounted for and 155,000 homeless.

The heavy rains that began last week have caused rivers to flood, inundating whole towns and destroying roads and bridges.

Rain is forecast to let up on Thursday but then continue through the weekend.

Climate experts attributed the extreme rainfall in Rio Grande do Sul to the confluence of a heatwave caused by this year’s El Niño phenomenon, which warms the waters of the Pacific and brings rain to southern Brazil; a weaker cold front with rain and gales coming from the Antarctic; and unusual warmth in the Atlantic also raising humidity.

Global warming exacerbates these phenomena and intensifies the effects between such systems, making weather unpredictable, said Marcelo Schneider, a National Meteorology Institute (Inmet) researcher.

ELECTRICITY CUTS

In Porto Alegre, a city of 1.3 million inhabitants, downtown streets were under water after the Guaiba River breached its banks with record water levels.

Porto Alegre residents faced empty supermarket shelves and closed gas stations, with shops rationing sales of mineral water. The city distributed water in trucks to hospitals and shelters.

The floods have also impacted water and electricity services, with more than 1.4 million affected overall, according to Civil Defense.

Almost half a million people were without power in Porto Alegre and outlying towns as electricity companies cut off supplies for security reasons in flooded neighborhoods. National grid operator ONS said five hydroelectric dams and transmission lines were shut down due to the heavy rains.

The city’s airport, its apron under water, has suspended all flights since Friday.

Fuel shortages were reported as state-run oil company Petrobras said it was having trouble moving diesel from its refinery in badly-flooded Canoas within metropolitan Porto Alegre, a senior government official said.

President Luiz Inacio Lula da Silva said on a government television program that the extent of the damage will not be known until the waters subside. He promised federal aid for the state in what is considered its worst ever climate disaster.

JP Morgan economists projected that the impact of the floods on Brazil's economy would be a modest dent in GDP growth and a marginal increase in inflation, mainly due to higher prices for rice that is largely produced in Rio Grande do Sul. The government said Brazil will import rice to stabilize the market.

Besides destroying critical infrastructure, the heavy rains and flooding have left grains fields under water and killed livestock, interrupting the soy harvest and halting work at multiple meat plants.

The Rio Grande port, a major port for grain exports, was operating normally, the state’s port authority said. However, main access roads were impassable, disrupting grain deliveries to the port as trucks had to make a wide detour, exporters said.