Prognostic Discussion for Monthly Outlook 
NWS Climate Prediction Center College Park MD 
300 PM EDT Mon Aug 31 2026 
 
 
30-DAY OUTLOOK DISCUSSION FOR SEP 2026 
 
The updated September temperature and precipitation outlook is primarily 
informed by model guidance across time scales including short- and medium-range 
(next 7 days), extended-range and subseasonal-range forecasts. Near coast sea 
surface temperatures (SSTs) and surface wetness anomalies adjust the outlook in 
some areas. 
 
There are considerable changes in the updated temperature outlook from the mid 
month outlook. Troughing is forecast to impact much of the western contiguous 
U.S. (CONUS) early in the month and so cooler conditions are now expected in 
these areas. The area of favored above-normal temperatures is shifted eastward 
to encompass the central U.S., Great Lakes and mid-Atlantic in the outlook 
update. There is now a slight tilt for below-normal monthly mean temperatures 
for a small region in the Pacific Northwest and Equal-Chances (EC) is now 
forecast in remaining areas as cooler than normal conditions to start the month 
may be offset during the second half of the month. 
 
Elevated odds for above-normal temperatures remain for the southern tier of the 
U.S. and Southeast Alaska. The highest likelihood for above-normal temperatures 
is forecast for the central Great Plains where the GEFS and ECMWF model 
guidance predict strong ridging during much of the first ten days of September 
as well as substantially below-normal surface wetness conditions. 
 
Potential troughing in the Northeast along with favored above-normal 
precipitation increases uncertainty and so Equal-Chances (EC) for above-, near- 
or below-normal temperatures are forecast in this area. For Alaska, troughing 
forecast in proximity to the state supports elevated odds for below-normal 
temperatures for parts of western and northern Alaska. 
 
There are also substantial modifications in the updated precipitation outlook 
from the earlier release in mid-August. Above-normal monthly total 
precipitation amounts remain favored for California and much of the 
Intermountain West, Rockies and Southwest. For the Pacific Northwest and parts 
of the northern Rockies, however, above-normal precipitation is now favored due 
to troughing over approximately the first ten days of the month. The greatest 
odds are forecast for areas in Oregon where significant precipitation is 
forecast over the next 7 days and where the monthly precipitation climatology 
is lower than nearby areas. 
 
In the short-term, tropical moisture elevates odds for above-normal 
precipitation for the southern half of the Florida Peninsula and heavy rains 
from Potential Tropical Cyclone 5 increases the likelihood for parts of 
southeast Texas. 
 
Enhanced precipitation on the northern periphery of subtropical ridging 
highlighted in the mid-month outlook is shifted northeastward in the updated 
outlook. Model guidance is consistent in predicting ridging to be more 
amplified in the central CONUS and so elevated odds for above-normal 
precipitation is now focused for the eastern Great Lakes and much of the 
Northeast. Forecast ridging in the central U.S. for much of the first ten days 
of September limits precipitation potential and tilts the odds to below-normal 
precipitation for areas in the central Plains and central Mississippi Valley. 
 
Model guidance across multiple time scales supports the weak tilt for 
below-normal precipitation for a small area along the central Atlantic 
coastline. There are only slight changes from the mid-August outlook for the 
state of Alaska. 
 
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***** Previous mid-month outlook discussion ***** 
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El Nino 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 Nino 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 Nino 
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 Nino 
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 Nino 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 Nino 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. 
 
The next monthly outlook...for Oct ... will be issued on Thu Sep 17 2026 
 
These outlooks are based on departures from the 1991-2020 base period. 
$$