How to read an IMD seasonal outlook map: terciles in plain words

IMD's seasonal outlook maps look like a patchwork of colours. Here is how to read one in under a minute.

Three equal buckets. IMD splits past rainfall into three equal groups, called terciles: below normal, normal and above normal. With no other information, each has a 33.33% chance. IMD states this on its maps.

The forecast tilts the odds. Each coloured patch shows the category that is most likely in that area, and the shade shows how likely. For example, in its 29 May 2026 update, IMD gave the South Peninsula a 45% chance of below-normal monsoon rain, 34% normal and 21% above normal.

White is not "normal". IMD notes that white areas on land mean no signal from the model. Treat them as the usual equal odds.

Odds, not promises. A 45% chance of below normal still leaves a 55% chance of normal or above. A forecast map tells you which way the dice are loaded, not how they will land.

How it played out. The South Peninsula ended the 2026 monsoon at 76% of its long-period average, its fourth lowest since 1901 (IMD, 30 September). The tilt was right this time, but that is not guaranteed every season.

Use these maps for planning, such as storing water or choosing crop timing, together with IMD's weekly extended-range forecasts and local advisories.

Join the El Niño help room on soshyal.com to ask questions and share what you see in your area.