Striking videos show streets, tunnels and São Paulo Metro stations in Brazil flooded after hailstorms and wind gusts

São Paulo experienced a sudden weather emergency on Wednesday, 14 October. Heavy rain, hail and strong wind gusts caused widespread flooding. The event disrupted roads, underground routes and the city’s Metro system. It mattered because the water rose quickly, trapping people, vehicles and public transport in several locations.

The Anhangabaú tunnel, in the city center, was flooded almost halfway to the ceiling. Cars floated instead of touching the road, while a truck was submerged up to its front windows. More than twenty vehicles and two public transport units were reportedly trapped there. Water also poured down the stairs of a Metro station like a cascade.

The mayor, Ricardo Nunes, said that 40 percent of the rain expected for the entire month fell within minutes. Several Metro lines were affected, and 24 flights were canceled at Congonhas Airport. The reports show how quickly intense weather can disrupt transport across a major city.

The article does not define hailstorms, but a hailstorm is a storm that produces falling pieces of ice called hail. Hail forms inside powerful thunderclouds, where strong rising air currents lift water droplets into very cold regions. The droplets freeze and grow as more water collects around them.

The same storm can also create intense rain and powerful wind gusts. When the cloud contains a lot of moisture, large amounts of water can fall quickly. Strong air movement within and around the storm can produce sudden gusts. These processes can happen together because they are driven by the storm’s vigorous vertical movement.

In São Paulo, witnesses reported hail, intense rain and strong gusts on 14 October. The combination caused rapid flooding in streets, tunnels and Metro stations. The event shows why a storm can become dangerous within minutes, even before transport systems can respond.

The mayor of São Paulo, Ricardo Nunes, said that 40 percent of the rain expected for the entire month fell in just a few minutes. This figure describes the storm’s concentration, not the total rainfall measured over the month. A large share of monthly rain arriving almost instantly can create dangerous conditions.

The sudden downpour produced flooding in streets and tunnels and affected several Metro lines. In the Anhangabaú tunnel, water rose almost halfway to the ceiling. Cars floated, a truck was covered up to its front windows, and more than twenty vehicles became trapped. The rainfall also contributed to wider transport disruption.

The reported comparison explains why the storm overwhelmed parts of São Paulo so quickly. It also helps show why the damage was not simply caused by ordinary rain. The article reports 24 canceled flights at Congonhas Airport and severe flooding in underground routes and stations.

The article reports the effects but does not explain the atmospheric mechanism. In general, a thunderstorm grows when warm, moist air rises quickly into a colder part of the atmosphere. Water droplets can freeze there, while other droplets remain liquid. This creates conditions for hail and very heavy precipitation.

Strong rising and sinking air currents help organize the storm. Rising currents support hailstones, while descending air can spread outward when it reaches the ground, producing intense wind gusts. When the cloud holds abundant moisture, rain can fall in a concentrated burst. These processes can develop within minutes in a powerful storm.

São Paulo’s storm showed the combined impact. Hail and gusts accompanied intense rain, which flooded streets, tunnels and Metro stations. Mayor Ricardo Nunes said 40 percent of the month’s expected rain fell within minutes. That concentration left little time for transport systems or drivers to react.

The article shows that underground transport spaces are especially exposed when water arrives suddenly. Tunnels, underground roads and Metro stations are lower than nearby surfaces. Rainwater can flow toward them from surrounding streets. Once inside, the water has fewer natural escape routes and can rise rapidly in an enclosed space.

The Anhangabaú tunnel illustrates the danger. Water reached almost halfway to the roof, while cars floated and a truck was submerged to its front windows. At a Metro station, water poured down the stairs in a cascade and covered the floor. These openings allowed surface water to enter lower areas quickly.

The storm also affected several Metro lines, showing that flooding can spread beyond one roadway. Because 40 percent of the expected monthly rain fell within minutes, systems had little time to manage the surge. Underground transport therefore became a major point of disruption during the emergency.

The flooding caused major transport disruption and created a serious public safety emergency. Vehicles were trapped or displaced, roads became impassable, Metro services failed in several areas, and air travel was interrupted. A report shared in the article also stated that one person died, although the article provides no further details.

Inside the Anhangabaú tunnel, cars floated, a truck was covered up to its front windows, and more than twenty vehicles were trapped. After the water fell, one gray car was shown resting partly on a taxi. Two buses remained stuck beside the road. Water also rushed down Metro station stairs and affected several lines.

The storm’s impact extended beyond the roads. The article reports that 24 flights at Congonhas Airport were canceled. These consequences followed rain that reached 40 percent of the expected monthly amount within minutes, leaving drivers, passengers and transport operators facing rapidly changing conditions.

The article describes flooding but does not explain drainage systems. In general, cities use street drains, channels and underground pipes to collect rainwater. Gravity carries the water toward larger channels or other designated outlets. This system works best when rainfall arrives at a manageable rate and the pathways remain available.

Intense rain can overwhelm drainage in two ways. The rainfall may deliver more water at once than drains and pipes can carry. Water may also flow quickly toward low points, such as tunnels and underground stations, where it accumulates. In São Paulo, the Anhangabaú tunnel filled rapidly, and Metro stairs carried water downward like a cascade.

Mayor Ricardo Nunes said 40 percent of the expected monthly rain fell within minutes. That sudden volume helps explain the widespread flooding in streets, tunnels and Metro areas. The event shows why concentrated storms can disrupt transport even when drainage infrastructure is operating normally.