Heavy rain in July 2025 Texas floods locally intensified by human-driven climate change

Contact Authors

• Davide Faranda, IPSL-CNRS, France  📨davide.faranda@lsce.ipsl.fr    🗣️English,French, Italian

• Mireia Ginesta, Oxford Sustainable Law Programme, University of Oxford, UK mireia.ginesta@smithschool.ox.ac.uk English, Spanish, Catalan

• Tommaso Alberti, INGV, Italy  📨tommaso.alberti@ingv.it 🗣️ English, Italian

Citation

• Faranda, D., Ginesta, M., & Alberti, T. (2025). Heavy rain in July 2025 Texas floods locally intensified by human-driven climate change. ClimaMeter, Institut Pierre Simon Laplace, CNRS. https://doi.org/10.5281/zenodo.15829357

Press Summary

• Meteorological conditions similar to that causing floods in Texas  are up to 2 mm/day (up to 7%) wetter  in the present than they have been in the past. 

• This event was associated with very exceptional meteorological conditions.

• Natural variability alone cannot explain the increase in precipitation associated with Texas floods.

Event Description

In the early hours of July 4, 2025, Central Texas was struck by a catastrophic flash flood event, with the heaviest rainfall hitting Kerr County around 4 a.m. The remnants of Tropical Storm Barry collided with a stalled frontal boundary over the Hill Country, producing torrential downpours that overwhelmed rivers and creeks. In the area surrounding Hunt, including the Camp Mystic site along the Guadalupe River, over 10 inches of rain fell within just a few hours, causing the river to rise explosively—nearly 29 feet in under an hour—between 4:00 and 5:00 a.m. At that same time, a group of young girls and their counselors were asleep in riverside cabins at Camp Mystic. The floodwaters arrived with such speed and force that many had no time to evacuate. Survivors described being awakened by thunder, screams, and eventually the sound of walls breaking apart as the river tore through the camp. Emergency alerts—including overnight warnings and a flash flood emergency issued at 4:03 a.m.—were not received by all residents due to poor cell coverage, and Kerr County had not activated a countywide emergency push alert system despite multiple watches and warnings in the preceding days. By sunrise, the tragedy was evident: dozens of people were missing, and the camp was devastated. The extreme speed of the river’s rise, combined with a lack of warning infrastructure, turned the event into one of the deadliest single-night disasters in the state’s recent history. The Guadalupe River had reached levels not seen since 1987, and rescue efforts, complicated by blocked roads and drone interference, began as day broke.

The meteorological conditions on July 4, 2025, during the Texas floods were characterized by slightly negative surface pressure anomalies over Central Texas, with values ranging up to –2 hPa, indicating the presence of a weak low-pressure system over the region. Temperatures were significantly below the climatological average for this time of year, with anomalies reaching –5 °C across much of the area affected by the flooding. Precipitation was highly concentrated over the Hill Country region, especially near Round Rock and the surrounding area, where daily accumulations exceeded 100 mm/day, highlighting the extreme nature of the event. Wind speeds during the flood event were also elevated, with strong southerly flow over the core impact zone, and maximum values exceeding 30 km/h. These winds may have contributed to enhanced moisture advection from the Gulf of Mexico. The data used in this analysis come from the ERA5 reanalysis, which integrates model simulations with in-situ and satellite observations to provide a physically consistent reconstruction of past atmospheric conditions. Localized discrepancies with station data may occur, particularly in areas of complex terrain or where observation density is low.

Climate and Data Background for the Analysis

In the IPCC AR6 report, Chapter 12, assigns high confidence to positive observed trends in extreme precipitation over Central and Eastern North America. Moreover, there is high confidence that high precipitation will increase over the same area with ongoing global warming. Intense convective episodes over this region are not uncommon in the spring, when convective activity is also heavily influenced by natural sources variability, with the greatest contribution coming from ENSO. In particular, a situation of decaying El Niño as observed during spring of 2024, is linked to an enhanced occurrence of severe weather outbreaks in this region. It is worth noting that the ENSO index we use does not distinguish a decaying El Niño from other neutral phases. 

Our analysis approach rests on looking for weather situations similar to those of the event of interest having been observed in the past. For this event we have low confidence in the robustness of our approach given the available climate data, as the event is very exceptional in the data record.

ClimaMeter Analysis 

We analyze here (see Methodology for more details) how events similar to the meteorological conditions leading to the July 2025 Texas floods have changed in the present (1987–2023) compared to what they would have looked like if they had occurred in the past (1950–1986) in the region [103°W 93°W 25°S 35°S]. Surface pressure changes show no relevant differences between the two periods, with near-zero anomalies over most of the affected region. Temperature changes show increases of up to +1.5 °C southern to the flood-affected area, particularly around Round Rock and extending toward the Gulf Coast. Precipitation changes reveal a general increase in rainfall totals, with present-day conditions up to 2 mm/day wetter in parts of Central Texas, especially along the corridor from San Antonio to Austin. Wind changes display enhanced wind speeds of up to +2  km/h across the region impacted by the flooding, notably over the inland areas west of Round Rock.

Similar past events do not show a clear seasonal shift, apart from a slight increase in June occurrences during the present period compared to the past. Changes in urban areas reveal that Round Rock experienced significantly warmer (+1.5 °C) and wetter (+1  mm/day) conditions during this event compared to similar past situations, Austin showed slight changes, while Killeen displayed the largest increase in precipitation (up to +1.5 mm/day). These results suggest that meteorological conditions similar to those of the July 2025 Texas floods are becoming more favorable for extreme precipitation, in line with what would be expected under continued global warming. 

Finally, we find that sources of natural climate variability, notably the El Nino Southern Oscillation and the Atlantic Multidecadal Oscillation, may have influenced the event. This suggests that the changes we see in the event compared to the past may be due to human-driven climate change, with a contribution from natural variability.

Conclusion

Based on the above, we conclude that meteorological conditions leading to the July 2025 floods in Texas  are up to 2 mm/day wetter (up to 7%) compared to similar past events. Natural variability alone cannot explain the changes in precipitation associated with this very exceptional meteorological condition.