Nino 3.4

Indices

The Nino 3.4 index is the sea surface temperature anomaly averaged over the Nino 3.4 box. It sits where changes in ocean temperature move the tropical rain the most, so it tracks ENSO impacts well.

NOAA builds its official indices (ONI, RONI) from it. The app also shows faster versions: weekly (NOAA OISST) and daily (Climate Reanalyzer). See Daily, weekly and monthly values.

How to read it

+0.5 °C or more = El Nino-like; +1.5 °C or more = strong. One warm week is not an El Nino: the official indices use 3-month averages.

Why it matters for Koh Samui

The app's ENSO factor for Samui uses the highest of the latest ONI and the latest weekly Nino 3.4 anomaly.

Sources

• NCAR Climate Data Guide -- Nino SST indices
• NOAA CPC -- index data files

Related

• ONI (Oceanic Nino Index)
• RONI (Relative Oceanic Nino Index)
• The Nino regions (1+2, 3, 3.4, 4)
• Daily, weekly and monthly values
• Factor: El Nino (event strength)

ENSO status now

ONI (NOAA CPC)

+1.80 °C, JJA 2026 (previous +1.39 °C)

RONI (NOAA CPC)

+1.36 °C, JJA 2026

Nino 3.4 weekly (NOAA CPC / OISST)

+3.0 °C anomaly, week of 16 Sep 2026 (SST 29.6 °C)