El Nino refers to the periodic warming of central and eastern Pacific ocean surface temperatures. These patterns commonly last 9 to 12 months and recur every two to seven years or an irregular schedule.
El Nino brings warmer, drier weather to the northern US and Canada, while the southern US remains cooler and wetter. In contrast, La Nina typically leads to cooler northern temperatures, heavy rain in the Pacific Northwest, and warmer, drought prone winters in the South. La Nina conditions are expected to transition to ENSO-neutral between May and July.
There is a 62% chance El Nino will emerge between June and August 2026, and persist through the end of the year. Unlike the record-breaking, strong El Nino of 2023-24, the upcoming 2026 pattern is forecast to be fairly weak.
However, early winter (October-December) could be warmer than average, but likely not as extreme as the record-breaking 2023-24 season. While E1 Nino usually suggests drier weather, Wisconsin has been trending wetter overall, therefore, a weak El Nino may not be strong enough to reverse that trend. If warmer temperatures persist, early winter precipitation is more likely to fall as rain rather than snow.
Periods of El Nino and La Nina generally last nine to 12 months but can sometimes extend for years. The two typically alternate back and forth and occur every two to seven years, but there is no regular schedule.
