"Chance of rain " is another way for the weather man to cover his azz.
Any given probability number is practically meaningless. What is the difference between 20% of chance of rain and 40% chance of rain, as far as you are concerned ?
In both cases it might or might not rain. The corollary is 80 % or 60 percent no chance of rain. hahaha
They hardly ever say there will be a 100% of this or that.
Gardeneer