PDSI Index (Palmer Drought Severity Index)
PDSI Index - Current situation - February 2025
According to the PDSI index, at the end of February there was a significant decrease in the area in meteorological drought, in the weak drought class, with only a small part of the Western Algarve remaining.
In terms of percentage distribution by class of the PDSI index in mainland Portugal, at the end of February there were:
- 33.3 % in the low rainfall class
- 65.5 % in the normal class
- 0.6 % in the low drought 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