PDSI Index (Palmer Drought Severity Index)
PDSI Index - Current situation - June 2026
According to the PDSI index, at the end of June there was a very significant change in drought conditions in mainland Portugal, with a generalized transition from wet or normal conditions in May to dry weather conditions in more than half of the territory in June. This way, the rain classes disappear from the continental territory, becoming predominant the normal class in the North and part of the Center and, at the same time, there is a weak expansion of drought, which covers practically the entire territory south of the Montejunto-Estrela system and also extends to some counties of the northern coast. Occasionally, there are still areas of moderate drought in the counties of the extreme southeast of the territory.
Percentage distribution by PDSI index classes:
- Normal: 36.2
- Weak Drought: 61.1
- Moderate drought 2.7
Drought monitoring
- Summary and about
Legend
PDSI Index (Palmer Drought Severity Index) was developed by Palmer (1965) and implemented and calibrated for mainland Portugal (Pires, 2003).
This index is based on the concept of the water balance taking into account data on the amount of precipitation, air temperature and available water capacity in the soil and allows the detection of periods of drought by classifying them in terms of intensity (weak, moderate, severe and extreme).
Table - Classification of the PDSI index for dry and rainy periods
Color legend
PDSI Classes
Description
greater than or equal to 4,0
Extreme rain
Extreme rain
3,00 to 3,99
Severe rain
Severe rain
2,00 to 2,99
Moderate rain
Moderate rain
1,00 to 1,99
Weak rain
Weak rain
-0,99 to 0,99
Normal
Normal
-1,99 to -1,0
Weak drought
Weak drought
-2,99 to -2,0
Moderate drought
Moderate drought
-3,99 to -3,0
Severe drought
Severe drought
less than or equal to -4,00
Extreme drought
Extreme drought