El Nino Watch
NOAA's official monthly odds of El Nino, neutral or La Nina, and of how strong El Nino will be, for the next 9 seasons.
Forecasts and bulletins
Each month (2nd Thursday) a team at NOAA's Climate Prediction Center publishes two tables. The first gives the chance of La Nina, neutral and El Nino for 9 overlapping 3-month seasons (ASO = Aug-Sep-Oct, SON, ...). The second splits those chances into strength classes, measured by the relative Nino 3.4 index (RONI).
Limits. Strength of the index does not guarantee strength of the local impact. The outlook is a human consensus of models, updated only monthly. 0% is rounded: it means very unlikely, not impossible.
Numbers are percentages and each row adds up to 100. Strength classes by the index value: weak +0.5 to +1.0 C, moderate +1.0 to +1.5 C, strong +1.5 to +2.0 C, very strong at or above +2.0 C (the same steps for La Nina below zero). Red bars = El Nino, grey = neutral, blue = La Nina. In September 2026: 97% chance of a very strong El Nino for Sep-Nov.
The stronger the El Nino, the more likely its typical effects in Thailand: a weaker, later rainy season, then a hotter and drier dry season (Feb-May), water shortages on Samui, haze and coral bleaching. The later seasons show when NOAA expects the event to end.