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PDSI Index (Palmer Drought Severity Index)
PDSI Index - Current situation - February 2026
According to the PDSI index, as of the end of February, there was no meteorological drought in mainland Portugal, although rainfall conditions had worsened, particularly in the municipalities of the North, Central, and Upper Alentejo regions, almost all of which are now in the most severe category (extreme rainfall).
The percentage distribution by PDSI index classes in mainland Portugal at the end of February is as follows:
- 75.1% in the extreme rainfall class,
- 24.5% in the severe rainfall class,
- 0.4% in the moderate rainfall class.
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
Last 12 month evolution
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Copyright © Portuguese Institute for Sea and Atmosphere 2026
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