Prognostic Discussion for Monthly Outlook 
NWS Climate Prediction Center College Park MD 
830 AM EDT Thu Aug 20 2026 
 
 
30-DAY OUTLOOK DISCUSSION FOR SEP 2026 
 
El Niño conditions in both the ocean and atmosphere have continued to 
strengthen entering mid-August 2026. Sea surface temperatures (SSTs) are near 
or greater than +3 degrees C in the equatorial eastern Pacific and the latest 
weekly Nino3.4 SST index value is +1.8 degrees C. A vast reservoir of 
above-normal ocean temperatures exists along the equator from the Date Line 
eastward to the South America coast to a depth of 200 meters. The atmospheric 
response to these ocean characteristics has been quite strong, namely enhanced 
convection over the central and eastern Pacific, strongly reduced Trade Winds 
and upper-level anticyclonic circulations symmetric about the equator. 
 
Response to the El Niño conditions is the primary driver of anomalous 
upper-level divergence, convection and winds in the global Tropics. Any 
Madden-Julian Oscillation (MJO) related forcing is minor in this context and 
given the time of the year. Below-normal surface moisture conditions encompass 
much of the Contiguous United States (CONUS) with severe, extreme and 
exceptional drought conditions as defined by the U.S. Drought Monitor covering 
many areas across the western U.S., Great Plains and coastal Southeast. 
 
The September Temperature Outlook favors above-normal monthly mean temperatures 
for the western CONUS, the southern Plains, the Southeast, and Southeast 
mainland Alaska and Southeast Alaska (i.e., Panhandle). Equal-Chances (EC) for 
above-, near- and below-normal temperatures are forecast for the Northern 
Plains, Midwest, Northeast and parts of the Ohio Valley and Mid-Atlantic. The 
greatest probabilities for warmer than normal temperatures are forecast for the 
north-central Rockies and Intermountain West. Dry surface conditions, dynamical 
and hybrid model guidance from the North American Multi-Model Ensemble (NMME) 
and Copernicus Climate Change Service (C3S) suites, the Seasonal Forecast 
System (SFS)-Beta and very strong positive (warmer) long-term temperature 
trends strongly support the forecast for above-normal temperatures. 
 
The above outlined factors and model guidance also support the Southern Plains 
and Southeast forecast for above-normal temperatures. Potential El Niño 
influence (i.e., slight tilt toward cooler than normal temperatures), closer to 
normal surface conditions and considerable spread in forecast guidance 
including that targeting the Week 3-4 period, particularly from the European 
Centre for Medium-Range Weather Forecasts (ECMWF) model, is the reason for the 
EC forecast area. Throughout the summer months, frequent troughing and cooler 
temperatures has impacted this area. The forecast in this region will be 
refined with the updated monthly outlook later this month. 
 
Below-normal SSTs off the coast of the Pacific Northwest lower the odds for 
above-normal temperatures for near coast areas in this region.  Potential for 
above-normal precipitation over the Southwest U.S. and southern Rockies lowers 
the likelihood for above-normal temperatures in this area. For Alaska, El Niño 
conditions, above-normal SSTs in the Gulf of Alaska and the majority of model 
guidance support the above-normal temperatures depicted for much of the state. 
EC is forecast for remaining areas due to considerable forecast guidance 
spread. 
 
Ongoing El Niño conditions, statistical, dynamical and hybrid model guidance 
and positive (wetter) long-term precipitation trends  support the favored wetter 
than normal conditions across the western CONUS. NMME, C3S and SFS-Beta model 
guidance is utilized for the forecast in interior Alaska and elevated odds for 
below-normal precipitation in the Pacific Northwest and western Great Lakes. 
The signals  from the model guidance noted here are quite weak and marginally 
linked to potential El Niño impacts. 
 
The slightly elevated likelihood for above-normal precipitation over the Ohio 
Valley, Central Plains and central Mississippi Valley is primarily based on 
general persistence from what we have observed much of the recent couple of 
months. Subtropical ridging across the southern tier of the U.S. has been 
overall quite persistent while shifting zonally. In association with this 
ridging, enhanced rainfall has occurred on the northern periphery of the ridge 
due to residual surface boundaries and mesoscale convective system (MCS) 
activity. 
 
FORECASTER: Jon Gottschalck 
 
The climatic normals are based on conditions between 1991 and 2020, following 
the World Meteorological Organization convention of using the most recent 3 
complete decades as the climate reference period.  The probability anomalies 
for temperature and precipitation based on these new normals better represent 
shorter term climatic anomalies than the forecasts based on older normals. 
 
An updated monthly outlook... for Sep will be issued on Mon August 31 2026 
 
These outlooks are based on departures from the 1991-2020 base period. 
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