A stretch of the Pacific Ocean warmed up by less than one degree, and weather forecasters around the world changed their plans. Here's what that means.
On June 11, 2026, NOAA's National Weather Service announced that El Niño has formed in the tropical Pacific and issued an El Niño Advisory.
Basis: NOAA, “El Nino forms, expected to strengthen, say NOAA forecasters” (June 11, 2026)
The rule is surprisingly precise. NOAA declares an El Niño when water in the equatorial Pacific runs 0.5°C above average for several months in a row — and the air above it behaves a certain way too. Half a degree of ocean, plus the sky.
Basis: Same NOAA release (definition of El Niño)
Forecasters expect it to strengthen to moderate or strong by fall, with a 63% chance that temperatures pass 2.0°C above average — the level NOAA calls a “very strong” El Niño.
Basis: Same NOAA release (strengthening forecast and 63% probability)
Forecasters also watch the air above that water, for a huge east-to-west flow called the Walker Circulation. Ocean and sky are read together, not separately.
Basis: Same NOAA release (Walker Circulation is monitored alongside sea surface temperature)
📊 Sources for the rankings mentioned in this note (links to the original data and retrieval dates) are on each quiz page below.