January 2025 Climate Forecast Discussion for the period Feb-Apr 2025 through May-Jul 2025
**Note: ** The IRI seasonal forecasts of precipitation and temperature issued this month are based on an objective calibration procedure that combines the NCEP-CFSv2, CanSIPS-IC4, COLA-RSMAS-CESM1, GFDL-SPEAR, and NASA-GEOSS2S models. 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 December 2024, negative sea surface temperature (SST) anomalies intensified over the central-eastern equatorial Pacific Ocean, leading to a NINO3.4 anomaly index value of -0.62 °C. The weekly-averaged SST anomalies in the NINO3.4 region were -0.7 °C for the week centered on Jan 08, 2025. This indicates onset of La Niña conditions in the equatorial Pacific Ocean. According to the early-January CPC ENSO forecast, a La Niña Advisory has been issued and La Niña conditions are expected to continue through February-April 2025 (59% chance), with a transition to ENSO-neutral likely during March-May 2025 (60% chance). The Indian Ocean Dipole (IOD) index is neutral (though negative), and the North Atlantic Ocean continues to exhibit persistent warm sea surface temperature (SST) anomalies.
IRI’s seasonal precipitation forecasts issued in January 2025 indicate moderately elevated chances of above-normal rainfall over parts of the northwestern and Midwestern United States, Central America, Siberia, northern South America, the Maritime Continent, and parts of Australia during February-April 2025. These probabilities gradually weaken during March-May, April-June, and May-July 2025 across the aforementioned regions. An increased likelihood of above-normal precipitation is also forecasted for South Asia and Southeast Asia during March-May, April-June, and May-July 2025, coinciding with the onset of the Southwest monsoon season in the region. Conversely, an increased probability of below-normal precipitation is forecasted for most of the Southern United States and Mexico throughout the forecast period. This trend of below-normal precipitation is also expected over various parts of South America, including the tropical northeast, southern Chile, and the Middle East during the forecast period, although the probability is relatively weak. Many of these precipitation patterns align with historical La Niña events and are consistent with the La Niña forecast for boreal winter and spring of 2025, though not all patterns necessarily conform to typical La Niña conditions and other regional and local factors can also play significant role in the evolution of seasonal climate anomalies.
Regarding temperature, most land areas are forecasted to have significantly higher probabilities of above-normal temperatures throughout the forecast period. However, parts of western Canada and Alaska show slightly elevated probabilities of below-normal temperatures during February-April 2025, though these probabilities are weak. The temperature forecasts also indicate slightly increased chances of below-normal temperatures in certain regions: Parts of South Asia (e.g., southern Indian Peninsula) and Southeast Asia during March-May, April-June, and May-July 2025. This may be related to above-normal precipitation during the pre-monsoon period, and various regions of Australia throughout the forecast period. It is important to note that these below-normal temperature probabilities are generally weak, except for the more pronounced forecast in western Canada and Alaska during Feb-Apr, 2025.
