Recent studies have investigated whether both the amplitude and key characteristics of El Niño–Southern Oscillation (ENSO) events have been changing, potentially due to some natural and/or anthropogenic change in the tropical Pacific Ocean state during recent decades (e.g., Yeh et al. 2009; Lee and McPhaden 2010; Newman et al. 2011; McGregor et al. 2013). If so, when might this change be identifiable in individual ENSO events? Was the extreme warmth in the equatorial Pacific seen in the recent 2015/16 El Niño, particularly near the dateline (L’Heureux et al. 2017), a harbinger of this change? To address these questions, we assess this event using statistics of Niño3 (5°N–5°S, 150°–90°W) and Niño4 (5°N–5°S, 160°E–150°W) sea surface temperature (SST) indices, derived from observational datasets and coupled general circulation model simulations. We use two indices to capture differences between events, important to both forecasts and diagnosis of ENSO and its impacts (Compo and Sardeshmukh 2010; Capotondi et al. 2015).