← extremewx.org · What a typical year looks like (top map), and how it differs in El Niño or La Niña years (bottom map). An ENSO year runs from June of the developing year through May of the next (1997–1998 = June 1997 – May 1998), the twelve months over which an event usually grows, peaks and decays. Choose the whole year, a season, or a single month with the bar above the maps. Drag or zoom either map and both follow; click a box to see every year's value there below. The years in each composite come from NOAA's Relative Oceanic Niño Index, plotted at the bottom with every El Niño and La Niña year marked. Related: TC climatology & trends · U.S. severe weather, 2° grid · Email me with bugs or requests.