June 2026 Climate Forecast Discussion for the period July-September through October-December 2026
**Note: ** The CCSR/IRI seasonal forecasts of precipitation and temperature issued this month are based on an objective calibration procedure that combines the output from four models: NCEP-CFSv2, CanSIPS-IC4, COLA-RSMAS-CESM1, and NASA-GEOSS2S-2. The climatological base period for normal is 1991-2020. The SST anomalies cited below refer to the OISST.v2.1 SST data set. Starting from June 2024, the observed climatology used to compute the dry mask was updated to 1991-2020, and the criterion modified to mask points where 10% of the training sample (i.e. 3 or more years) received less than or equal to 1 mm over a 3-month season.
During May 2026, sea surface temperature (SST) anomalies increased further across the central-eastern equatorial Pacific Ocean, with the monthly Niño 3.4 index reaching +0.94 °C. The past four weekly Niño 3.4 index values (20 May–10 June) ranged from +0.9°C to +1.5°C, consistently exceeding the El Niño threshold and confirming the presence of moderate El Niño conditions across the tropical Pacific. The early June CPC ENSO forecast, issued under an “El Niño Advisory,” indicates that the El Niño conditions are present and expected to strengthen into the Northern Hemisphere winter 2026-27. (It is important to note that ENSO monitoring and prediction issued by CPC is now based on the relative Niño 3.4 index). The Indian Ocean Dipole (IOD) index is currently in a neutral state. The North Atlantic registered a value of +0.18 °C, while the South Atlantic showed gradually increasing warming, reaching +0.32 °C in April 2026. The Pacific Decadal Oscillation (PDO) index recorded a value of -1.60 °C in May 2026.
The CCSR/IRI objective Multi-Model Probability Precipitation Forecast for July–September (JAS) 2026 indicates strongly increased odds of below-normal precipitation (yellow to brown shading) across northern South America, Central America and the Caribbean, the Indian Peninsula, Southeast Asia, parts of Australia, and the Maritime Continent. This dry signal persists through August–October (ASO), September–November (SON), and October–December (OND), although its strength and spatial extent vary by region. During SON, an area of increased probability for below-normal precipitation emerges over southern Africa and strengthens further during OND. In JAS, enhanced odds of below-normal precipitation are also indicated over Ethiopia and the southwestern Arabian Peninsula. In contrast, during JAS and ASO, the southwestern United States and adjacent Southern Plains show increased probabilities of above-normal precipitation, with this wet signal extending and strengthening into the southern United States during SON and OND. From ASO through OND, odds also tilt strongly toward above-normal precipitation over Uruguay and central Chile, as well as parts of northeast Africa, the Middle East, and Southwest Asia. In particular, strongly increased probabilities of above-normal precipitation over the Middle East and Southwest Asia. While many of these precipitation signals are broadly consistent with developing El Niño conditions in the central–eastern Pacific expected to mature during the summer and early fall of 2026, not all regional anomalies are necessarily directly linked to the evolving ENSO state.
The temperature forecasts indicate a high likelihood of above-normal temperatures (red shading) across much of North America, northern and central Eurasia, the Middle East, Asia, the Maritime Continent, and large parts of Africa and South America throughout the forecast period. In the July–September and August–October seasons, areas of increased probability for below-normal temperatures (blue shading) emerge over parts of southeastern Australia. However, during the final two forecast seasons, these cooler-than-normal signals weaken and are replaced by an increased likelihood of above-normal temperatures across the region.
