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 by that correction; they were separately revised on 13 August — see the note under the table.)
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 | −0.504 |
| Grid cells with SPEI-3 below −0.5 | 51.1% (579 of 1,132) |
Source: GlobMaps drought climatology, Vietnam, May 2026 update.
Correction, 13 August 2026. The May 2026 figures above were revised on this date. The underlying drought files were recomputed on 9 August 2026, and a month-scoped re-read of them (verification runs 31711356352 and 32024730295, the second re-run under a check that requires every probe to report that it actually ran) returns Thailand −0.376 / 37.9%, Vietnam −0.504 / 51.1%, Malaysia −0.327 / 39.0%. Earlier versions of this page carried the original May computation — −0.288, −0.487 / 46.6% and −0.398 / 34.4%. The cell totals (718, 1,132, 698) are unchanged, and the counts past the line (272, 579, 272) come from the same run log. One part of this is not yet explained. Malaysia’s mean rose from −0.398 to −0.327 — that is, towards wetter — while the share of cells past the −0.5 line rose too, from 34.4% to 39.0%. A move towards a wetter average would normally push that share down. Both rising means the shape of the distribution changed, not only its centre, and we do not yet have an account of why. Vietnam and Malaysia also moved by nearly the same amount (+4.5 and +4.6 percentage points), which reads as systematic rather than incidental. We are publishing the verified figures and this open question together rather than the figures alone.
The national mean sits just above the −0.5 line — but the distribution matters more than the average. Just over 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 terms, and in Thailand's weighting SPEI supplies half the score. Which component pulls Kon Tum and Gia Lai below the 0.20 line is a question about their vegetation and soil-moisture inputs specifically, and we have not read those, so we are not going to explain the gap here. The divergence itself 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. What May 2026 gives is a dated reading, not a trajectory: the composite index found no drought class in either province at that point in the season. Whether that holds is what 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.