这里的like并不是动词“喜欢”的意思了,而是介词,意思是“像.”,常与be搭配,be like,意思是像.,what is weather like=how is the weather like 是介词,介词后面必须有名词,作它的宾语,构成介宾结构,
what在英语中相当于名词,所以,符合介宾结构；
how在英语中只是副词,作状语.
变成陈述句就是：
The weather is like what today.
The weather is how today.