Event replay
Walk through a past El Niño or La Niña month by month for one country, and see how it compared with every other observed event.
What am I looking at?
The Teleconnections maps answer "what does an El Niño typically do?" by averaging every past event into one seasonal picture. This page asks the opposite question: what actually happened during one particular event? Nothing is averaged into seasons here. You get the real monthly sequence, from January of the year the event began through December of the year it ended, which puts the peak in the middle and shows the build-up and the decay either side.
The faint grey lines behind each chart are every other observed event of the same type, lined up so that month 0 is January of each one's own first year. That is what makes "was this one unusual?" answerable: if the coloured line sits outside the grey band, this event was doing something the others did not. The dates along the bottom belong to the selected event, the coloured line; each grey line is running through its own years at the same point in its own sequence.
Every impact on this page is observed: sea surface temperature from the ENSO indices, rainfall from CHIRPS, heat from ERA5. The one exception is drawn so it cannot be mistaken for anything else: where the selected event is still running, the sea-surface-temperature panel also carries the live forecast from ECMWF SEAS5 and Météo-France System 9, dashed and in their own colours. The rainfall and heat panels stop at the observed record, because there is no calibrated forecast of country rainfall or heat behind this site.
This event
Comparison
By sub-national region
Sea surface temperature, Niño 3.4
The event itself, in standard deviations. This is the index the event was classified from, so it is the same everywhere and does not depend on the country chosen.
Heaviest 10-day rainfall
The wettest ten consecutive days in each month, the index behind flood risk. Computed within each calendar month, so a spell crossing a month boundary is split between the two.
Longest dry spell
The longest run of days below 1 mm inside each month. A missing day breaks a spell rather than extending it.
Maximum temperature
Monthly mean of the daily maximum, averaged over the country.
Rainfall
Monthly total over the country, and the departure from a neutral year for that same calendar month.
Dry days
Days below 1 mm. The seasonal maps show the longest dry run; inside a single month that is ambiguous because spells cross month boundaries, so this counts days.