Peru & Ecuador coast
Flooding / extreme rain
Warm coastal waters drive torrential rain, flash floods and landslides. Historically the hardest-hit zone of any El Niño.
Guayaquil · Piura · Trujillo · Lima
Bulletin
Weekly bulletin
This week's Pacific numbers, in plain language.
What the equatorial Pacific did this week, in NOAA numbers and plain language, plus the regions most likely to feel it.
NOAA observation week:
Published by El Niño Observatory
Analysis generated:
This week's take
Little change this week. Weekly Niño 3.4 anomaly held near +3.4 °C versus +3.3 °C last week. Ocean data, not a local weather warning.
Weekly Niño 3.4: +3.4 °CTraditional ONI: +2.16 °C · JAS 2026
In the central equatorial Pacific (Niño 3.4), the weekly sea-surface temperature difference from the 1991–2020 average is +3.4 °C. This reading alone does not establish an event's official strength.
NOAA's current ENSO advisory and RONI
In February 2026, NOAA CPC adopted the Relative Oceanic Niño Index (RONI). Traditional ONI and weekly temperatures use different averaging methods; they are not interchangeable measures of event strength.
NOAA's current ENSO advisory and RONI ↗Niño 1+2
+5.2 °C
SST 26.3 °C
Niño 3
+4.3 °C
SST 29.4 °C
Niño 3.4
+3.4 °C
SST 30.1 °C
vs +3.3 °C last week
Niño 4
+1.1 °C
SST 29.8 °C
The ocean this week
For the week of October 21, 2026, Niño 3.4 stood at +3.4 °C (SST 30.1 °C). That is +0.1 °C from last week's +3.3 °C. Niño 1+2 was +5.2 °C, Niño 3 +4.3 °C, and Niño 4 +1.1 °C. 8-week trend: warming.
What that means
Significantly warmer than normal conditions in the eastern and central Pacific are historically associated with a range of global weather patterns. These effects can vary greatly depending on the time of year and specific location.
What to watch next
It's important to keep an eye on NOAA's official advisories for any changes in the El Niño status. Local weather forecasts and civil protection agencies will provide the most relevant information for your area.
Regions most likely affected
Places with a documented El Niño link, ranked using this week's NOAA readings. Not official warnings.
Southern Brazil, Uruguay & NE Argentina
Flooding / extreme rain
A strengthened subtropical jet brings persistent extreme rainfall. The 2023-24 Rio Grande do Sul floods are the textbook example.
Porto Alegre · Pelotas · Santa Maria · Florianópolis
Amazon & Northeast Brazil
Drought / water / fire risk
Fewer rain-producing storms bring severe drought, record-low rivers, fires and crop failure across the Amazon basin and the semi-arid Northeast.
Manaus · Santarém · Belém · São Luís
Central America: Dry Corridor
Drought / water / fire risk
Failed rains across the Dry Corridor threaten subsistence maize and bean harvests, deepening food insecurity.
Guatemala City · San Salvador · Tegucigalpa · Managua
Indonesia & Malaysia
Drought / water / fire risk
Severe drought dries peatlands, fueling large forest fires and haze that drifts across borders; rice and palm yields fall.
Jakarta · Palembang · Pontianak · Surabaya
Eastern Australia
Extreme heat
Reduced rainfall and heatwaves raise bushfire danger and strain water supplies along the populous east coast.
Brisbane · Sydney · Canberra · Melbourne
Earlier weeks
Numbers: NOAA CPC weekly OISST and Oceanic Niño Index. The interpretation is our own.
Historical observations may be revised by NOAA. The seasonal index includes only seasons completed by this observation week. These are NOAA's current figures, not the numbers as first published.