September 12, 2026 · Sources: NOAA Climate Prediction Center, NWS Sacramento, NIFC, DWR, and press reporting
Bottom line
A potentially historic El Niño is strengthening, and the odds tilt toward a warmer and wetter than normal winter for Sacramento — but the local historical record under El Niño is genuinely mixed, and one or two atmospheric rivers will likely decide the season.
The setup: a very strong event
Odds of "very strong" El Niño
>90%
for fall/winter 2026–27 (NOAA CPC, September outlook)
Odds it's the strongest since 1950
75%
Oct–Dec index at or above +2.5°C (up from 69% in August)
Eastern Pacific sea-surface anomalies exceed +3.0°C (Niño-1+2 at +3.4°C, Niño-3.4 at +1.8°C), with subsurface anomalies above +10°C at depth.
El Niño is given a 100% probability from fall 2026 through early 2027, tapering through spring. La Niña odds are effectively zero into spring.
Peak is expected October–December, most likely November, with the greatest California effects December through March. Next CPC update: October 8.
The Sacramento caveat
The National Weather Service Sacramento office stresses there is little historical correlation between ENSO phase and Northern California precipitation — Southern California's link is far stronger.
Of seven past strong El Niño winters, the Sierra saw 3 wet, 2 dry, and 2 near-normal outcomes.
UC Berkeley's Central Sierra Snow Lab examined nine strong/very strong El Niños: 4 produced above-median snowfall, 3 below, 2 near the median. The lab calls this winter "still a toss-up."
CPC's December–February outlook favors above-normal precipitation across most of California (strongest in the south) and above-normal temperatures in Northern California — warmth that can turn lower-elevation snow into rain and runoff.
Stronger events tilt the odds: research puts the 95th percentile of northern California winter precipitation at 178% of normal during strong El Niños. But it guarantees nothing.
Atmospheric rivers: the wildcard
Scripps researchers call atmospheric rivers the "precipitation wildcards" — one or two can make the winter; a weak AR season breaks it. Seasonal AR counts can't be predicted.
Past dry El Niño years (1977, 1987, 2007, 2013, 2015) were defined by deficient AR activity; the classic wet years (1983, 1998) were AR-driven.
The flood stakes for the Valley: roughly 80% of Central Valley levee breaches are linked to atmospheric rivers, with at least 162 Delta levee failures in the past century across 1,100+ miles of often century-old levees.
El Niño is also forecast to raise California coastal sea levels about a foot by mid-October, coinciding with king tides — a flooding risk for low-lying Bay Area communities.
Rest of 2026: fire season
Nationally, 8.2 million acres burned by August 31 — 166% of the 10-year average — and Sacramento logged its warmest March on record.
NIFC's September outlook: fire potential above normal in September for far northern/northeastern California, but normal for most of the Sacramento Valley, returning to normal October–December. Offshore wind events are the wildcard.
What water officials are doing
No winter water-supply forecast exists yet — the initial State Water Project allocation for Water Year 2027 is due December 1, 2026. Reservoirs entered the water year at about 114% of average, so the starting position is decent.
The state's posture is dual flood-and-supply preparation: 14 flood-flow diversion partnerships with pre-deployed pumps for groundwater recharge, forecast-informed reservoir operations being formalized at Oroville and New Bullards Bar, and $219 million more committed to Sites Reservoir in August.
Sacramento's flood system is getting its first major Sacramento Weir upgrade in 108 years — a 1,500-foot passive weir — targeting 200-year flood protection.
As the Sacramento Suburban Water District puts it: "No forecast can tell us exactly what the Sacramento region will experience this winter."