Peru identified a cutoff low as the weather system behind the southern highland rains. SENAMHI also says El Niño-context ocean warming intensified that system, while describing the precipitation as not a direct effect of El Niño. Its contribution at Machu Picchu remains unresolved.
In July we documented how El Niño Costero reached Peru months before NOAA declared the basin-wide Pacific event. Now Peru has another measurable impact: disruptive August rain around Machu Picchu, during the region’s normally dry season.
This is a narrower piece than that one. The July article explained the Costero-versus-basin-wide distinction and catalogued coastal damage through mid-year. This is one documented event, and the useful thing about it is how cleanly Peru’s own agencies separated the weather system that caused it from the climate state it happened inside.
On Tuesday 18 August, the Dirección Desconcentrada de Cultura de Cusco suspended visitor access to the Inca Trail network at Machu Picchu, effective Wednesday 19 August and until further notice.
Its executive director, Maritza Rosa Candia, said intense and unusual rain had been falling since the night of Monday 17 August, causing landslides, streams running high, flooding of campsite areas, collapse of sanitation facilities, damage to pontones (the footbridges the route depends on) and soil erosion. Eleven sectors were named: Llulluchapampa, Ayapata, Paqaymayu Alto, Soqtacocha, Yuncachimpa, Qonchamarka, Wayllabamba, Pawkarcancha, Cusichaka, Phuyupatamarka and Wiñaywayna.
Hikers who had started on 18 August were ordered to turn back. Alternate access at kilometre 104 (Chachabamba) and kilometre 106 (Choquesuysuy) was placed under evaluation, subject to conditions through 22 August, with entry fees to be rescheduled or refunded if the closure held. Archaeologist Francisco Huarcaya, who leads conservation on the trail network, said surveillance staff were monitoring the affected sectors continuously.
Separately, Peru’s civil defence institute logged the wider district emergency. INDECI Report No. 10743, issued 19 August at 06:57, records that at 10:00 on 18 August intense rain increased the flow of the Huayruro and Chaquimayo rivers until both overflowed, producing flooding that caused material damage to homes and transport infrastructure in the communities of Huayllabamba, Choquellusca and Tarayoc, Machupicchu district, Urubamba province.
That report covers the district emergency rather than the trail itself, and its damage list is not a trail-by-trail inventory. Read together, though, the two documents establish something firmer than most claimed El Niño impacts arrive with: a dated hazard, named watercourses, named communities, itemised damage and an administrative response.
SENAMHI, Peru’s national meteorological service, identified DANA Aníbal as the immediate synoptic system affecting southern Peru. DANA stands for Depresión Aislada en Niveles Altos, an isolated depression at high levels, the Spanish-language term for a cutoff low. That does not exclude a background contribution from El Niño, and as the next section shows, SENAMHI does not exclude one.
SENAMHI describes a DANA as a cold atmospheric system sitting between 5 and 10 kilometres up, typically over the Pacific near Peru and Chile. Critically, it also describes what the system does: it facilitates the transport of moisture from the Amazon toward the Andes. As the cold air mass moves inland it meets warm, humid air arriving from the Amazon basin, and that interaction produces the precipitation, mainly above about 3,800 metres, with snow above 4,000.
The service has named these systems since 2026, alternating male and female names alphabetically: Aníbal, Bertha, Carlos, Diana, and onward. Aníbal brought rain, sleet, hail, snow and gusts to around 45 km/h across the southern highlands, with red alerts standing in Tacna, Moquegua and Arequipa, and effects reaching the central sierra.
A cutoff low is a synoptic-scale feature: a parcel of cold upper-level air that detaches from the main atmospheric flow and can produce substantial precipitation when moisture and instability are present. El Niño is an ocean-atmosphere state on the timescale of seasons. Both can be true of the same rainfall, and neither is a synonym for the other. The interesting question is never which one it “really” was, but how much the second changed the first.
SENAMHI addressed this directly, and its answer is more careful than either the sceptical or the alarmed version.
Spokesperson Grinia Ávalos said the recent precipitation is not a direct effect of El Niño, but that warming of the sea has intensified the DANA. She noted that Aníbal’s arrival coincides with the installation of El Niño, which has enhanced precipitation intensity in the region, and that ocean warming in the El Niño context increases atmospheric humidity and instability. Her direct quote, as reported: “Because of the warming of the sea in the context of El Niño, those drizzles have been significantly exacerbated.”
One scope limit matters enormously here. Ávalos was speaking about persistent drizzle on the coast, in southern Lima districts such as Villa El Salvador, Chorrillos and San Juan de Miraflores. She was not describing Machu Picchu. Her statement establishes that Peru’s weather service sees El Niño amplifying this DANA’s precipitation somewhere. It does not establish by how much, or whether the same amplification applies 600 kilometres inland on the Amazon-facing slope of the Andes.
The Costero question is worth answering plainly. Machu Picchu lies on the Amazon-facing side of the Andes, outside the coastal zone where Niño 1+2 warmth most directly favours convection, and Niño 1+2 stood at +2.9°C in July. Coastal warming alone therefore does not explain this event, although broader oceanic conditions may still influence the moisture and circulation around the Andes.
Layered rather than either/or:
The fourth item is not a hedge. Answering it is a specific technical exercise, a probabilistic event-attribution study, and nobody has run one on this event. Meanwhile the basin-wide backdrop has genuinely shifted since our July piece: CPC’s 9 July discussion gave 81 percent odds on a very strong event, and its 13 August discussion gives greater than 90 percent, with a 69 percent chance of a historic event in October–December. The Southern Oscillation indices ran near two standard deviations negative in July. A stronger, better-coupled event is a plausible amplifier. It is still not a measured contribution.
An ENFEN or SENAMHI technical bulletin quantifying August precipitation anomalies in the southern sierra against climatology, rather than the word “unusual.” A published attribution analysis. Or a pattern: repeated dry-season disruptions through September and October rather than one system, which would say more than any single event can.
Until then, the honest summary is the one Peru’s agencies have already published. The immediate weather system has a name: DANA Aníbal. Whether El Niño made its rainfall more likely or more intense at Machu Picchu remains unresolved.