On 7 March, 2025, Bahía Blanca, Argentina, skilled an unprecedented rainfall occasion with over 300 mm of rain in simply 8 hours, almost half of the town’s annual common. This excessive occasion, the heaviest within the metropolis’s recorded historical past (1956-present), was attributable to a chilly entrance reaching the world after a number of days of sizzling, humid climate. Per week earlier, Bahía Blanca had already obtained greater than 80 mm of rain, which can have contributed to soil saturation earlier than the flooding. A bigger area, together with the capital Buenos Aires, had been experiencing excessive warmth since mid-February, with temperatures exceeding 40°C in northern Argentina, southern Brazil, Paraguay, and Uruguay. Between 19 February and eight March 2025, 61 cities in central-north Argentina recorded heatwave situations. 

The acute rainfall on March seventh affected over 300,000 folks, with 16 reported deaths, 1,400 being displaced (A24, 2025) and two individuals nonetheless lacking (La Nación, 2025). The harm estimated within the metropolis quantities to 400 million USD (Ámbito, 2025). On the identical time, warmth alerts had been issued in 15 provinces, with document temperatures within the north (Buenos Aires Herald, 2025, SMN Argentina by way of X). Buenos Aires confronted blackouts and visitors disruptions affecting lots of of 1000’s attributable to peak vitality demand (International Occasions, 2025, AP Information, 2025). Whereas no knowledge on heat-related mortality is out there on the time of writing, previous occasions have proven elevated mortality dangers related to occasions like this (Chesini et al., 2019; Chesini et al., 2021, Pinotti et al., 2024).

To evaluate to what extent human-induced local weather change altered the probability and depth of the heavy precipitation resulting in the extreme flooding, in addition to the intense warmth researchers from Argentina, Kenya, the Netherlands, Sweden, Denmark, Mexico, the US and the UK undertook an attribution examine for the intense rainfall in probably the most affected area, that coincides with the world the place flood warnings had been in place (Fig. 1a), in addition to for the intense seasonal warmth within the wider space (Fig. 1b). For this bigger area we additional calculate the warmth index, a mix of excessive temperatures and humidity to evaluate the position of local weather change within the heatwave immediately previous the intense rainfall (Fig. 1c). In Argentina, the impacted areas had been affected by rainfall that occurred intermittently between 1-7 March. We due to this fact studied modifications within the wettest 7-day interval over the examine area. The warmth was particularly intense in February and March, however early sizzling spells since January resulted in your complete season being exceptionally heat which is  essential for understanding the general impacts, so we give attention to the summer season season (December to March) for the temporal definition of the warmth occasion. 

Determine: (a): 7-day amassed rainfall throughout 1-7 March 2025, primarily based on MSWEP knowledge. The examine area is highlighted in purple. The scatter plots present the rainfall accumulations for a similar interval from 25 climate stations by the Nationwide Climate Providers (NWS). (b) The common of each day most temperature throughout 1 Dec 2025 -18 March 2025, primarily based on MSWX dataset. The examine area (SouthEast South America area or the SES area) is highlighted in blue. (c) Common Warmth index (HI) throughout 15 Feb-7 March, 2025, primarily based on ERA5 dataset. The blue spotlight reveals the SES area.

Primary findings

• In Northern Argentina, together with the Buenos Aires province and CABA, intensified and extra frequent excessive warmth and heavy rainfall occasions in addition to simultaneous or sequential extremes like heat-heavy rainfall or hot-dry occasions heighten the danger of compounding hydrometeorological hazards. CABA’s growing older inhabitants, city growth, and excessive inhabitants density enhance each publicity and vulnerability to those hazards.
• Nearly 50% of the city inhabitants is employed within the casual economic system and a big proportion of the city livelihoods are delicate to local weather shocks e.g. attributable to employment disruption and publicity to warmth.
• Based mostly on gridded reanalysis merchandise, we discover that the intense warmth occasion is comparatively uncommon, anticipated to happen in as we speak’s local weather about as soon as each 50 to 100 years. Nevertheless, in a 1.3°C cooler local weather, excessive warmth resembling noticed in the summertime 2024/25 would have been just about unimaginable. When repeating the evaluation for the shorter sizzling and humid warmth wave immediately previous the rainfall occasion, we discover a equally giant position of human-induced local weather change. 
• Local weather fashions additionally present that local weather change is making such temperatures rather more frequent and intense. Nevertheless, the rise within the fashions is smaller than in reanalysis merchandise and thus seemingly underestimating the impact of local weather change. However, wanting on the future, fashions present a really robust pattern that will increase with future warming, rendering such an occasion a standard prevalence in a 2.6°C hotter local weather in comparison with pre-industrial. 
• The affect of local weather change on the rainfall occasion is far much less clear. Whereas all the 35 out there climate stations within the space present a rise within the depth of heavy rainfall of between 7-30% related to world warming of 1.3°C, this isn’t represented in any of the out there gridded reanalysis merchandise which present on common a reducing pattern. 
• Local weather fashions are largely in settlement with the station knowledge and on common present a rise within the probability and depth of heavy rainfall resembling noticed in early March. The same enhance in most, however not all, fashions is seen for an extra 1.3°C warming, representing a 2.6°C local weather. 
• Station knowledge and mannequin knowledge each present an rising pattern in excessive rainfall with rising temperatures, which can be what is anticipated for rainfall occasions of this type in a warming local weather. Thus, it’s seemingly that local weather change elevated the probability and depth of the heavy rainfall. Nevertheless as station knowledge and gridded knowledge don’t agree on the signal of the pattern we can’t reconcile the 2 and make a conclusive assertion.
• These consecutive occasions spotlight the broader challenges of managing more and more frequent and intense hazards within the province, the place vulnerabilities are formed by urbanization, infrastructure inadequacies, and social inequalities.
• As excessive climate occasions grow to be extra widespread, it is very important hold investing in early warning techniques, climate-smart city planning, and preparedness that takes a number of hazards into consideration. For example, creating extra inexperienced and blue areas may also help scale back warmth in cities, present reduction throughout sizzling climate, and decrease the danger of flooding—all of which will be achieved even in crowded city areas.