United States
Three seasonal systems over the same ground, month by month, with the skill of each one's own reforecast beside it — and a straight answer about where American seasonal forecasts are worth acting on.
What the systems say
1 October 2026 · routes 10 · 03 · 02Temperature
| Target | lead | SEAS5 | C3S multi-system | NMME | |||
|---|---|---|---|---|---|---|---|
| P(above) | skill | P(above) | skill | P(above) | skill | ||
| October 2026 part elapsed | +0 | 44% | 85% | 44% | 98% | 40% | 96% |
| November 2026 | +1 | 26% | 54% | 36% | 60% | 32% | 61% |
| December 2026 | +2 | 37% | 41% | 38% | 56% | 35% | 56% |
| January 2027 | +3 | 32% | 47% | 33% | 72% | 37% | 42% |
| February 2027 | +4 | 24% | 53% | 27% | 90% | 36% | 93% |
| March 2027 | +5 | 34% | 46% | 28% | 89% | 32% | 64% |
They are furthest apart on February 2027: NMME puts the odds of an above-normal month at 36% where SEAS5 puts them at 24% — 11 points between two systems reading the same ground for the same month. The skill column is the one that governs how much of this to believe: 54–61% of this box beat climatology at November 2026, and 46–89% by March 2027.
Rainfall
| Target | lead | SEAS5 | C3S multi-system | NMME | |||
|---|---|---|---|---|---|---|---|
| P(above) | skill | P(above) | skill | P(above) | skill | ||
| October 2026 part elapsed | +0 | 25% | 78% | 39% | 89% | 34% | 76% |
| November 2026 | +1 | 46% | 41% | 45% | 60% | 44% | 52% |
| December 2026 | +2 | 40% | 47% | 44% | 61% | 41% | 61% |
| January 2027 | +3 | 41% | 37% | 45% | 67% | 44% | 52% |
| February 2027 | +4 | 48% | 42% | 44% | 61% | 45% | 62% |
| March 2027 | +5 | 48% | 43% | 42% | 56% | 44% | 45% |
They are furthest apart on March 2027: SEAS5 puts the odds of an above-normal month at 48% where C3S multi-system puts them at 42% — 6 points between two systems reading the same ground for the same month. The skill column is the one that governs how much of this to believe: 41–60% of this box beat climatology at November 2026, and 43–56% by March 2027.
And what this site’s own engine says
Route 09skilful over 31% of the box
skilful over 32% of the box
skilful over 27% of the box
skilful over 27% of the box
skilful over 42% of the box
The Analog Bench does not appear in the table above, and cannot: it forecasts rolling three-month seasons where the others forecast months, and it publishes an anomaly in degrees where they publish a tercile probability. Holding those side by side in one row would be arithmetic on unlike quantities.
It is here because it carries one number nothing else on this site does. Signal is the anomaly with the warming trend taken back out — what the analogue years actually contribute beyond what you would get by drawing a straight line through the last forty. Where the two are close, the forecast is mostly the trend and deserves to be read as such. The analogues are drawn from the ocean state through July–August–September 2026.
The systems behind those numbers
Routes 10 · 03 · 02Official
The CPC outlooks
NOAA's Climate Prediction Center issues the United States' official monthly and seasonal outlooks on the third Thursday of every month, as tercile probabilities for temperature and precipitation, plus a seasonal drought outlook. They are the benchmark — not a competitor.
Dynamical
The NMME behind them
Eight coupled models from NOAA, NASA, GFDL, NCAR and Environment Canada, pooled into roughly a hundred members. The NMME is the single most useful thing to put next to a CPC map, because it shows you how much of the outlook is agreement and how much is one model.
European view
SEAS5 over North America
ECMWF's system covers the United States too, on a different model core with a different set of biases. Where SEAS5 and the NMME agree over North America, that is worth something; where they disagree, that is worth more.
Where US seasonal skill actually lives
Be honest about thisWinter temperature over the southern and eastern United States, in a year with a well-developed ENSO event, is about as good as mid-latitude seasonal forecasting gets — the Pacific jet is being pushed by something the models genuinely predict. Winter precipitation across the southern tier and the Pacific Northwest inherits the same signal.
Summer precipitation over the Corn Belt, by contrast, is close to unforecastable three months out, and any product that implies otherwise is over-selling itself. The useful summer signal is in soil moisture and the trend, not in the circulation.
Temperature outlooks almost everywhere carry a large and unglamorous contribution from the warming trend. That is real skill and it counts — but a site ought to tell you when the model is adding to it and when it is just riding it.