The same El Niño strength, a different winter.
Four strong El Niños followed a multi-year La Niña: 1957–58, 1972–73, 2009–10 and 2023–24. Across the Lower 48 they averaged – (–), against – for the other six strong El Niños (–). Germany was – against – (–, which survives the correction). Every El Niño after a multi-year La Niña since 1959 had a major sudden stratospheric warming (–, against – of all winters, – uncorrected). The storm track across the southern tier held in both groups: the southern Plains were wetter in – strong El Niños.
Four against six is a small sample: under a fair coin 4 of 4 happens one time in eight, and none of the U.S. region differences survives the correction across – tests. The PDO split rests on three positive-PDO strong El Niños. Read these as the shape of the record, not as probabilities.
The United States
nClimDiv 1950–2025Nine regions, the strong El Niño groups and the PDO split
Division by division
The PDO's thumb on the scale
Gershunov and Barnett (1998) showed that El Niño's North American winter pattern is stronger and more consistent when the North Pacific is in its matching (positive-PDO) phase and weaker when it is not; Maher et al. (2022) found the same in large model ensembles, roughly additive. The PDO has been negative in – months since January 2020 (NCEI ERSSTv5). In our record, strong El Niños with a negative PDO before them averaged – across the Lower 48 (–) and those with a positive PDO – (–): the expected direction, on three positive-PDO events, with no test passing. The PDO's own phase is partly set by ENSO, so a very strong El Niño can push it positive, as 1957 did; 2023–24 did not.
Sudden stratospheric warmings
ERA5, winters 1959–60 onA warming raises the odds of cold spells over the following weeks in the eastern U.S. and Europe; it does not decide the season. The live vortex and the model's many winters: The stratosphere.
Europe and the world
Snow and cold at the Season Book's stations
mixedWinter energy: demand, storage, prices
null resultsEnergy lives on this page and on heat because it follows the weather: heating demand in winter, cooling demand in summer. In winter the answer is a clear null. U.S. heating degree days, gas storage draws and winter gas and coal prices do not differ by regime (– tests pass; the smallest p for national heating demand is –). Storage levels, LNG exports and policy move winter gas far more than ENSO does. The one strong energy signal in these data is summer cooling demand the year after an El Niño peak.
What 2026–28 implies
The forecast view with confidence tiers: Fall/winter 2026–27 in context. Place by place: Winter Odds and every strong winter.