The box off Peru and Ecuador (0-10° S, 90-80° W). It warms first and most in eastern Pacific El Ninos, and swings a lot from week to week.
Indices
Nino 1+2 is the smallest and most eastern box, right along the South American coast. It reacts fast, so it is noisy. A warm Nino 1+2 alone (a "coastal El Nino") brings heavy rain to Peru and Ecuador but may have little effect on Asia.
In September 2026 the CPC reported Nino 1+2 at +3.4 °C.