Seasonal Rainfall Outlook Platform
Seasonal Rainfall Outlook Platform

September initialization · ECMWF SEAS5 calibrated with CHIRPS · ONDJ R3 (Deyr) rainfall domain

ONDJ 2026/27 rainfall outlook

Research reconstruction · not an official EMI or ICPAC forecastTarget period ongoing (ends 31 Jan 2027)

The forecast leans toward above normal rainfall in the ONDJ R3 (Deyr) rainfall domain: averaged over the area, the local probability of above normal is 58%, against about 33% for climatology. Mean forecast rainfall is 265 mm against a 1993/94–2024/25 average of 188 mm (+77 mm, +41%).

Average local probability

Below normal 16%Near normal 26%Above normal 58%

Each grid cell has its own tercile probabilities; these are their averages over the 100% of the area that has probabilities. They are not the probability that the area-total rainfall falls in a category.

Full ONDJ 2026/27 outlook and maps →

Map of ONDJ 2026/27 tercile probabilities for ONDJ R3 (Deyr) rainfall domain
Tercile probabilities, ONDJ 2026/27, ONDJ R3 (Deyr) rainfall domain. Open the map viewer below for other products. Smoothed for display; switch to Grid cells to see the values as computed.

Rainfall amount

Forecast mean265 mm
1993/94–2024/25 average188 mm
Anomaly+77 mm (+41%)

Amounts cover 100% of the area. They come from the amount-corrected ensemble, calibrated separately from the probabilities, so the two can differ slightly.

Forecast signal

Strong tilt toward above normal

Largest area-average probability 58%, compared with a one-third reference. The local climatological probabilities (observed tercile frequencies in the training years) are close to, but not exactly, one-third. Based on probabilities only.

Historical skill — ONDJ R3 (Deyr) rainfall domain

Moderate improvement over climatology (interval above zero)

Probability skill (RPSS) +0.133 for ONDJ, cross-validated 1993–2016 (95% interval +0.032 to +0.245); better than climatology in 18 of 24 years. One-target p = 0.010; adjusted for testing 5 targets (Holm), p = 0.040 (still significant). Details

Signal strength describes how far this forecast's probabilities depart from climatology. Historical skill describes how forecasts made the same way scored in past years. A strong signal is not a confidence rating.

ONDJ 2026/27 — September initialization: every target

What's new

  • How statistical downscaling is implemented · release 2026-10-19.0, 2026-10-19
    Display or explanatory-text change
  • Method selection with Benjamini-Hochberg · release 2026-10-17.3, 2026-10-17
    Change to the scientific method
  • Real-time issue from 2027, statistical downscaling, more statistical power, dry-season maps · release 2026-10-17.2, 2026-10-17
    Change to the scientific method · New evidence or diagnostics (method unchanged) · Display or explanatory-text change

All releases and the change log →

Other forecast cycles

All outlooks →

Research behind the method