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Prognostic Discussion for Long-Lead Hawaiian Outlooks
NWS Climate Prediction Center College Park MD
830AM EDT Thu Aug 20 2026
MONTHLY FORECAST DISCUSSION VALID SEPTEMBER 2026
Sea surface temperature (SST) anomalies ranging from -0.5 to +0.5 degrees
Celsius (C) were observed around the Hawaiian Islands (Kauai, Oahu, Maui and
the Big Island) during the previous week with warmer anomalies near the Big
Island and weaker anomalies near Kauai.
From January through July 2026, rainfall total accumulations were:
Lihue Airport 37.36 inches (189 percent of average)
Honolulu Airport 21.12 inches (241 percent of average)
Kahului Airport 28.21 inches (288 percent of average)
Hilo Airport 87.39 inches (137 percent of average)
Most climate models from the North American Multi-Model Ensemble (NMME) and the
International Multi-Model Ensemble (IMME/C3S) predict positive SST anomalies
around the Hawaiian Islands in September 2026. Based on model SST and surface
air temperature forecasts, above-normal temperatures are favored for Kauai
(Lihue), Oahu (Honolulu), Maui (Kahului), and the Big Island (Hilo).
For the September 2026 precipitation outlook, the probability of above-normal
precipitation is elevated for all islands of Hawaii, with greater probabilities
for southeastern islands and weaker probabilities for northwestern islands. The
outlook is consistent with most models from the NMME and IMME, as well as
statistical consolidation forecast tool (CCA/CA/ENSO-OCN).
TEMPERATURE PRECIPITATION
FCST AVE LIM FCST BLW MEDIAN ABV
Hilo A70 76.4 0.5 A55 8.0 9.3 11.0
Kahului A70 79.3 0.4 A50 0.1 0.2 0.5
Honolulu A70 81.8 0.4 A45 0.4 0.6 0.8
Lihue A60 79.4 0.3 A40 1.7 1.9 2.6
SEASONAL FORECAST DISCUSSION VALID SON 2026 - SON 2027
Refer to the prognostic discussion of the long-lead seasonal outlooks for the
contiguous U.S. (CONUS) and Alaska for further description of the El Nino
Southern Oscillation (ENSO) outlook and other climate conditions relevant to
the seasonal outlook.
El Nino conditions are observed over the tropical Pacific Ocean. Equatorial sea
surface temperatures (SSTs) are above average across the central and eastern
Pacific Ocean. Above-average subsurface temperatures have strengthened across
the east-central and eastern Pacific Ocean in the last two months. Enhanced
convection and precipitation was evident along the equator from near the Date
Line to the eastern Pacific, while suppressed convection and precipitation were
observed over the Philippines, Indonesia, and Papua New Guinea. Upper-level
wind anomalies were easterly from the western to the east-central equatorial
Pacific and westerly over the eastern equatorial Pacific. Low-level westerly
wind anomalies were evident from the western to the east-central equatorial
Pacific Ocean and wind anomalies were easterly over the eastern Pacific Ocean.
El Nino is strengthening, with a greater than 90% chance of a very strong event
during the Northern Hemisphere fall and winter 2026-27. Historically, El Nino
conditions favor above-normal precipitation for Hawaii in the boreal summer and
early autumn and below-normal precipitation in late autumn and winter seasons.
The Hawaii Seasonal Outlook for temperature and precipitation is based
primarily on dynamical model forecasts from the NMME and statistical forecasts.
The impacts of the current and predicted El Nino on the temperature and
precipitation for Hawaii are a primary driver of the Hawaii Seasonal Outlook in
most seasons.
Enhanced probabilities for above-normal temperatures are predicted in the
outlook for Oahu, Maui, and the Big Island from September-October-November
(SON) 2026 through November-December-January (NDJ) 2026-27, and for Kauai from
SON 2026 to October-November-December (OND) 2026. Below-normal temperatures are
forecast for January-February-March (JFM) 2027, supported by dynamical model
forecasts from the NMME and C3S. The outlook is also consistent with El Nino
impacts with the addition of decadal-timescale temperature trends for the
region. El Nino impacts tend to lead to cooler-than-average temperatures for
the northwestern islands of Hawaii as the winter progresses. Due to increasing
uncertainty in ENSO impacts and weakening signals in forecast guidance, equal
chances (EC) for above, near or below normal temperatures are indicated for
Oahu, Maui, and the Big Island in December-January-February (DJF) 2027 and for
Kauai from NDJ 2026 to DJF 2026-27. EC is also likely for all Hawaiian islands
beginning in February-March-April (FMA) 2027 and extending through longer leads.
In SON 2026, EC is indicated in the seasonal precipitation outlook for Kauai,
Oahu, Maui and the Big Island, due to weaker signals in forecast tools.
Below-normal precipitation is increasingly likely for all of Hawaii beginning
in OND 2026 and continuing through the March-April-May (MAM) 2027 season. This
is due to most dynamical and statistical seasonal precipitation forecast tools
and the historical relationship between a predicted strong El Nino event and
winter precipitation for the Hawaiian Islands. Due to uncertainty in forecasts
for longer leads (for the April-May-June (AMJ) 2027 season and beyond), EC is
indicated for all the Hawaiian islands for the precipitation outlook.
Hilo
TEMPERATURE PRECIPITATION
FCST AVE LIM FCST BLW MEDIAN ABV
SON 2026 A70 76.2 0.4 EC 24.3 30.2 40.8
OND 2026 A60 75.5 0.4 B40 28.3 34.5 42.0
NDJ 2026 A45 74.2 0.4 B60 26.4 36.6 43.0
DJF 2027 EC 72.8 0.4 B65 19.6 30.2 33.3
JFM 2027 B40 71.8 0.4 B65 22.0 32.0 44.5
FMA 2027 EC 71.7 0.4 B60 24.6 34.1 45.5
MAM 2027 EC 72.0 0.5 B50 22.5 28.4 34.0
AMJ 2027 EC 72.9 0.5 EC 21.4 23.7 29.0
MJJ 2027 EC 74.0 0.4 EC 20.2 27.5 29.1
JJA 2027 EC 75.2 0.4 EC 19.4 27.2 31.4
JAS 2027 EC 76.1 0.4 EC 25.2 28.6 33.4
ASO 2027 EC 76.4 0.4 EC 26.1 28.8 33.3
SON 2027 EC 76.2 0.4 EC 24.3 30.2 40.8
Kahului
TEMPERATURE PRECIPITATION
FCST AVE LIM FCST BLW MEDIAN ABV
SON 2026 A70 79.1 0.4 EC 2.1 3.3 4.8
OND 2026 A60 77.8 0.4 B40 4.2 5.3 8.1
NDJ 2026 A45 75.9 0.4 B60 5.2 7.6 9.5
DJF 2027 EC 73.8 0.4 B65 4.6 6.9 8.7
JFM 2027 B40 72.5 0.4 B65 4.2 6.2 8.2
FMA 2027 EC 72.3 0.4 B55 3.2 4.1 6.4
MAM 2027 EC 73.0 0.4 B45 2.5 3.5 4.6
AMJ 2027 EC 74.3 0.5 EC 1.2 1.6 2.2
MJJ 2027 EC 76.0 0.5 EC 0.7 1.1 1.8
JJA 2027 EC 77.7 0.4 EC 0.7 1.1 1.5
JAS 2027 EC 79.0 0.4 EC 0.8 1.1 1.6
ASO 2027 EC 79.4 0.4 EC 0.8 1.6 2.5
SON 2027 EC 79.1 0.4 EC 2.1 3.3 4.8
Honolulu
TEMPERATURE PRECIPITATION
FCST AVE LIM FCST BLW MEDIAN ABV
SON 2026 A70 81.4 0.4 EC 2.5 4.0 5.6
OND 2026 A50 80.0 0.4 B40 4.4 6.4 8.5
NDJ 2026 A40 77.7 0.5 B60 3.9 5.6 8.8
DJF 2027 EC 75.3 0.5 B65 3.7 5.6 8.6
JFM 2027 B40 73.9 0.4 B65 2.1 4.6 7.8
FMA 2027 EC 73.8 0.4 B55 1.9 3.2 4.7
MAM 2027 EC 74.8 0.4 B45 1.8 2.6 3.0
AMJ 2027 EC 76.3 0.4 EC 1.2 1.6 1.8
MJJ 2027 EC 78.2 0.4 EC 0.8 1.4 1.6
JJA 2027 EC 79.9 0.4 EC 0.7 0.8 1.3
JAS 2027 EC 81.3 0.4 EC 1.0 1.4 1.7
ASO 2027 EC 81.7 0.4 EC 1.6 2.4 3.1
SON 2027 EC 81.4 0.4 EC 2.5 4.0 5.6
Lihue
TEMPERATURE PRECIPITATION
FCST AVE LIM FCST BLW MEDIAN ABV
SON 2026 A70 79.1 0.3 EC 9.2 10.0 11.2
OND 2026 A50 77.8 0.3 B40 9.2 11.7 15.6
NDJ 2026 EC 75.7 0.3 B60 8.6 12.1 16.9
DJF 2027 EC 73.6 0.4 B65 7.5 8.4 14.0
JFM 2027 B40 72.2 0.4 B65 6.5 8.8 13.8
FMA 2027 EC 72.1 0.5 B55 5.8 8.4 9.9
MAM 2027 EC 72.8 0.5 B45 5.3 6.6 8.0
AMJ 2027 EC 74.2 0.5 EC 4.7 5.5 6.0
MJJ 2027 EC 76.0 0.5 EC 4.9 5.4 5.9
JJA 2027 EC 77.7 0.4 EC 4.4 5.3 6.9
JAS 2027 EC 79.0 0.3 EC 5.3 6.1 7.8
ASO 2027 EC 79.4 0.3 EC 6.2 7.9 8.4
SON 2027 EC 79.1 0.3 EC 9.2 10.0 11.2
FORECASTER: Luke He
Anomalies are based on the 1991-2020 means.
CLARIFICATION: EC indicated equal chances that the predicted parameter will
fall into any one of the three categories, whose boundaries are specific in the
tables above. A forecast specification of EC means there is no particulate tilt
of the odds toward above normal or below normal conditions in the outlook. For
example A40 means a 40% chance that the average temperature or total
precipitation will be in the above normal class, B40 means a 40% chance that
the average temperature or total precipitation will be in the below normal
class, and N35 means a 35% probability that the average temperature or total
precipitation will be in the near normal class. When EC is specified, all
categories are equally likely.
NOTE - These outlooks are intended for use prior to the start of the valid
periods. Within any valid period, observations and shorter range forecasts
should be consulted. Also, this set of outlooks will be superseded by the
issuances of the new set net month, on Thu Sep 17, 2026.
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