SPI
干旱类别
0.5 ≤ SPI
湿润
−0.5 < SPI ≤ 0.5
正常
−1.0 < SPI ≤ −0.5
轻旱
−1.5 < SPI ≤ −1.0
中旱
−2.0 < SPI ≤ −1.5
重旱
SPI ≤ −2.0
特旱