On 16 December 2021, a tropical depression made landfall on the eastern coast of Peninsular Malaysia, bringing torrential downpours throughout the peninsula for three days.

[16] Widespread damages were reported in the states of Selangor and Pahang, especially the district of Hulu Langat and the city of Shah Alam.

[18] On 14 December 2021, the Japan Meteorological Agency (JMA)[nb 1] upgraded a westward-moving low-pressure area to a tropical depression.

[24] By 21:00 UTC, the JTWC upgraded the system to a tropical depression, assigning it the designation 29W as it continued over marginally favorable developmental conditions.

[25] Shortly after, at 23:00 UTC, the depression made landfall north of the city of Kuantan in the state of Pahang, and began to weaken afterwards, prompting the JTWC to issue its final advisory on the system by the next day.

[34] The Klang Gates Dam released 25 per cent of its reservoir in stages after water levels exceeded acceptable ranges.

[36] Later that night, Tuan Ibrahim, the Minister of Environment and Water, released an emergency statement requesting immediate preparations at Kuala Lumpur from floods after the breaching of four main rivers across the city.

[37] The SMART Tunnel was activated amidst the increasing precipitation, and achieved record-high diversion volumes of approximately five-million cubic meters of flood water.

Health Minister Khairy Jamaluddin warned on 20 December that the disaster could lead to an increase in infections in the country.

The first death was reported that day, after the body of a factory operator—who had fallen off a motorcycle while riding through a flooded road—was discovered at 2:22 pm near a Chinese cemetery at Gambang.

Police have been deployed to the Sultan's Pier at Kota Bharu "to prevent crowds from going there to watch the rising river".

[58] Minor flooding prior to the landfall of 29W on 3 December left 140 people displaced at Setiu and Besut for several days.

[69] 93 water pumps were deployed to remove the floodwaters at the scene, while 134 floodgates were closed to prevent overflows from high tides.

[70] The main electrical substation at Glenmarie exploded during the night, causing a blackout across some parts of Shah Alam.

[74] At Kuala Lumpur, large tracts of Dataran Merdeka, Jalan Masjid India and Kampung Kasipillay were flooded.

[75] Flood waters between the main roads connecting the town of Meru and Bukit Raja were measured with a depth of 2 to 3 metres (6.6 to 9.8 ft).

Tenaga Nasional, the only electric utility company in Malaysia, announced power disruptions at 82 areas at Klang.

[80] The first death at the state was reported the same day, when a body was discovered 350 metres (1,150 ft) way from an apartment at Section 22 of Shah Alam.

[92] There was a lack of food for two days at the township, leading to looting at several inundated convenience stores and supermarkets during the afternoon of 20 December.

[93] Baharudin Mat Taib, Assistant Commissioner of the Shah Alam police chief, confirmed the reports.

[96] Floods in Pahang were initially reported in three villages at Kuantan during the late hours of 16 December, although the extent was minor.

[97] However, Maran and Raub suffered floods the same day after 48 hours of continuous rain, and by 8 pm almost 200 people were evacuated.

Roads linking to Kuala Tembeling, Felda Padang Piol, and several other villages were entirely cut off where floodwaters were measured to be 0.8 m (2.6 ft) deep.

Landslides were reported in several areas, notably at Kampung Amar Penghulu and Taman Eko Rimba Jeram Toi.

[17][147] There were complaints on social media that the authorities were slow in providing aid, with many victims relying on volunteers for food and basic necessities.

[148] Puan Sri Shariffa Sabrina Syed Akil, the president of a local conservation group, cited the slow response as a consequence of ineffective bureaucracy.

[149] The Prime Minister of Malaysia, Ismail Sabri Yaakob, publicly acknowledged certain "weaknesses" over the government's response towards the disaster.

In July 2023, the Shah Alam High Court dismissed both MBSA's and KDEB's applications to strike out the lawsuit, with Justice Mohd Zaki Abdul Wahab saying that there were issues that needed to be heard at a full trial.

[158] In order to mitigate this issue, aside from improving weather monitoring systems, experts and activists have urged action to be taken to reduce the effects of climate change.

[158] Moreover, this could involve reviewing the construction of infrastructure that will be affected by storms, flooding and rising sea levels, and granting international aid to help countries cope with climate change.