Look at the sky with salt. Can we see the weather with salt in real life?

A leaf knows spring, rather critical. The ancients often used phenology to predict the weather. With today's knowledge, we can at least measure the relative humidity of the air by looking at the sky with salt. I don't think people used to measure the weather with only one index. There must be many other additional factors, such as the season, the location of salt and so on.