simmer Jan dropped the sSPI for January, falling from the December's []{
   "SPI": 2.4,
   "date": "2022-12-01"
} to january's []{
   "SPI": 1.8,
   "date": "2023-01-01"
}.

请在不改变原有含义的基础上，修改上方句子使表达更加精简同时更加易于理解。
user
1月的SPI从12月的2.4降至1.8。
assistant