Correction, 11 August 2026. As first published, this article gave Kon Tum as "D2 — Severe Drought" and Gia Lai as "D1 — Moderate Drought". Both labels were wrong. The MDI values themselves (0.141 and 0.088) were right, but they were mapped to drought classes using the wrong thresholds, taken from a strategic brief rather than from the pipeline. Under the actual scale — MDI below 0.20 is None — neither province was in drought in May 2026. The province section and the summary below have been corrected; the national figures were unaffected and are unchanged.
Vietnam's Central Highlands grow most of Southeast Asia's coffee, alongside cassava and pepper. In the May 2026 GlobMaps drought update, Vietnam as a whole sits close to the drought threshold on a three-month view — while the two Highlands provinces most people would look at first, Kon Tum and Gia Lai, do not register a drought class at all. That gap is the story.
Vietnam-wide: the three-month signal is negative
SPEI-3 — the Standardised Precipitation-Evapotranspiration Index over a rolling three-month window — compares the recent water balance against the same season in the historical baseline. Readings below −0.5 are conventionally read as drought conditions.
| Indicator | Value (May 2026) |
|---|---|
| Vietnam SPEI-3, national mean | −0.487 |
| Grid cells with SPEI-3 below −0.5 | 46.6% (527 of 1,132) |
Source: GlobMaps drought climatology, Vietnam, May 2026 update.
The national mean sits just above the −0.5 line — but the distribution matters more than the average. Nearly half of Vietnam's grid cells are already past the drought threshold, which is exactly the situation a national average hides: the country reads "almost dry" while specific growing areas are well past it.
Kon Tum and Gia Lai: where the Highlands stand
MDI (Multi-Drought Index) folds the precipitation-evapotranspiration signal together with vegetation and soil-moisture indicators into a single province-level score, mapped onto the standard drought classes. The scale runs 0 to 1, and the first class boundary sits at 0.20: below that, the classification is None — no drought.
| Province | MDI (May 2026) | Severity |
|---|---|---|
| Kon Tum | 0.141 | None — No Drought |
| Gia Lai | 0.088 | None — No Drought |
Both provinces sit well under the 0.20 line, Gia Lai at less than half of it. On the composite index, the heart of the Highlands coffee belt was not in drought in May 2026.
Set that against the national picture in the table above and the two readings point opposite ways: nearly half of Vietnam's grid cells past the SPEI-3 drought threshold, and the two provinces everyone watches sitting at None. Both are correct, because they measure different things. SPEI-3 is a water-balance anomaly against the season's own history; MDI is a composite that also carries vegetation and soil moisture, and vegetation in an irrigated perennial crop does not fall over the moment rainfall does. The divergence is the signal worth carrying into a risk file — a single index, whichever one you happen to have, would have told you only half of it.
A Neutral ENSO label does not settle the question
The official relative index, RONI, read +0.47 for the AMJ 2026 season — below the +0.50 threshold. Basin-wide conditions are therefore Neutral, not El Niño. That is worth saying plainly, because the drought signal above does not depend on the label: SPEI-3 and MDI are measured from observed water balance and vegetation, not derived from an ocean index.
The 2018-19 El Niño cycle makes the point from the other direction. In that event Thailand's SPEI-3 stayed positive (roughly +0.135 to +0.703), and the regional picture was better than what the 2026 readings show. A named El Niño is not a prerequisite for regional dryness — and the absence of one is not reassurance.
Why this matters this season
Highlands coffee leans on irrigation through the dry months, and cassava draws down stored soil moisture across a long growing cycle. That irrigation is part of why the composite index reads None here while the national water-balance signal is negative: the buffer is doing its job in May. What it does not tell you is how much buffer is left, and that is the question the rest of the season answers.
For agricultural lenders and insurers, the practical unit is the province, not the country. A portfolio concentrated in Kon Tum and a portfolio spread across Vietnam carry different exposure to the same national average, and only the province-level view separates them.
What this analysis does not say
- It is not a yield forecast. A drought class describes water and vegetation conditions, not harvested tonnage.
- It says nothing about prices. Market outcomes depend on trade, stocks, and demand that this data does not observe.
- It is not a seasonal ENSO forecast. RONI +0.47 is the measured AMJ 2026 state, not a projection of what follows.
What it does give is a dated, province-level measurement of where drought stress actually sat in May 2026 — the sort of number you can put in a risk file and defend later.
We publish the province-level Southeast Asia drought picture as each monthly update lands. More at globmaps.com.