This preliminary study examines the definition problem and challenges of climate forecasting and disaster responses associated with the El Ni(n)o costero (coastal) of 2017,which developed rapidly with no wing and had catastrophic effects in Peru.Such a localized El Ni(n)o was not documented since 1925.An initial review suggests that in addition to the characteristics of the event (surprise),govment responses may have been inadequate (as media reported) because of conflicting forecast reports (U.S.and Peru),which provoked a hydrometeorological debate and stifled decision making.Partly to blame was the El Ni(n)o definition problem,which can cause uncertainty and affect perception of risk,depending on which region of the equatorial Pacific one uses to identify an event.Responses were further complicated by the fact that some regions within Peru were experiencing drought prior to the El Ni(n)o costero’s onset and impacts from the El Ni(n)o 2015-2016 were less than expected.Furthermore,a new govment was in place,which may have hindered action.Thus,El Ni(n)o costero provides lessons to heed,not only with respect to the forecast information,but also with reference to the context of the forecast and disaster setting,which can influence disaster responses to hydrometeorological threats.