2025 Precipitation Overview
- Early 2025: The Amazon basin experienced a below-average rainy season by January, with most states reporting less precipitation than normal. However, some regions (Acre, Amazonas, Pará, Tocantins) recorded average or slightly improved rainfall, which provided temporary relief to drought-affected areas. Notably, La Niña conditions—typically associated with increased rainfall—emerged in January, but global warming may have lessened their rain-boosting effect. While northern Amazon states (Amapá, northern/central Amazonas) saw near or above-average rainfall from February through April, river levels remained lower than historical norms, and the overall situation was uncertain.[1]
- February–March 2025: After an extended drought, the Amazon experienced heavy rainfall, causing destructive flooding, particularly impacting indigenous communities and local wildlife. Surplus precipitation conditions replaced the previous water deficit, with notable anomalies tracked in observed data.[2]
- Trend for 2024: The Amazon saw a dramatic reduction in rainfall—up to 70% less than expected—resulting in severe drought and extremely low river levels. These deficits persisted over much of the year, highlighting significant hydrological stress.[3][4][5]
Longer-Term Trends & Regional Patterns
- Historical Context (1980–2021/2022):
- Annual precipitation in the Amazon basin has fluctuated across datasets:
- CHIRPS data: Shows a statistically significant increase of 39mm/decade.
- GPCC, CRU, ERA5 data: Reveal slight increases or decreases, none significant except for CHIRPS.
- IMERG data (2001–2022): Registers a moderate decrease.
- These trends represent only minor changes compared to the basin's average of 2,200mm/year.[6]
- Recent 40-Year Cycles:
- Wet seasons have become 15–22% wetter.
- Dry seasons have gotten 5.8–13.5% drier.
- This amplified seasonal rainfall cycle increases risks of both flooding and drought.[7]
- Spatial Variability:
- Northern and western subregions tend to show increasing precipitation.
- Southern and southeast subregions face declining rainfall, with more pronounced dry seasons.[8][9][6]
- Deforestation continues to reduce regional precipitation: a 3.2% loss in forest cover (2002–2015) led to a 5.4% reduction in rainfall, especially during dry seasons.[9]
Hydrological and Ecological Impacts
- Persistent drought (especially in 2023–2024) drove river levels to historic lows, reduced water security for communities, and exacerbated fire hazards and agricultural losses.[4][5]
- Surges of rainfall in early 2025 temporarily eased drought but created flood risks—especially for vulnerable indigenous populations and biodiversity.[2]
Summary Table: Amazon Basin Precipitation Trends
Year | Rainfall Trend | Key Event | Ecological Impact |
2023 | Exceptionally low (drought) | Driest year in decades | Record-low river levels[4][5] |
2024 | ~70% below normal | Severe multi-regional drought | Water scarcity, fire, crop failure[3] |
Early 2025 | Below average overall | Gradual recovery, then flooding | Fluctuating river levels/floods[1][2] |
Past 40 years | Wetter wet seasons, drier dry seasons | Amplification of extremes | Increased floods & droughts[7][6][9] |
Key Takeaways:
- The Amazon basin experienced severe drought from 2023 through much of 2024, with rainfall up to 70% lower than expected. Early 2025 brought a partial reversal—average to above-average precipitation in some northern areas—culminating in flooding following earlier deficits.
- Over decades, rainfall across the basin shows mixed but generally minor long-term trends, with localized increases and decreases. Seasonality (wetter wet, drier dry) has intensified.
- Deforestation and climate change are major drivers of reduced dry season rainfall and increasing extremes. Hydrological impacts include greater risk of floods, droughts, and threats to local communities and biodiversity.[6][7][9]
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- https://www.acaps.org/fileadmin/Data_Product/Main_media/20250128_ACAPS_BRAZIL_-Impact_of_Drought_in_the_Brazilian_Amazon_and_2025_Outlook.pdf
- https://www.isciences.com/blog/2025/05/06/proof-point-surplus-following-drought-in-the-amazon-rainforest
- https://news.mongabay.com/2025/05/amazon-people-brace-for-a-drier-future-along-the-endangered-madeira-river/
- https://pmc.ncbi.nlm.nih.gov/articles/PMC10998876/
- https://www.worldweatherattribution.org/climate-change-not-el-nino-main-driver-of-exceptional-drought-in-highly-vulnerable-amazon-river-basin/
- https://www.nature.com/articles/s41598-025-87418-5
- https://phys.org/news/2025-06-tree-reveal-rainfall-seasonality-amazon.html
- https://www.bbc.com/news/articles/cd6qvpe0dxqo
- https://eos.org/research-spotlights/deforestation-is-reducing-rainfall-in-the-amazon
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