A rainy season can be called “rains.” “Rains” is plural, but “rain” is singular.
I enjoyed visiting the city in the famous rains of spring.
I would ask “Do you ride your bike in the rain?” “In rains” is rather awkward there. When we refer to a weather condition generally, we usually use the definite article and the singular.
He takes walks in the snow.
I don’t go out in the cold.
I can’t run in the heat.
We had a picnic in the rain.
Of course, it helps that some of those aren’t countable.
“Hair” is singular. “Hairs” is plural, but you would not likely tell someone they had beautiful hairs. Without specificity, the word “hair” by itself is understood to mean the hair on your head. And the word “hairs” rarely refers to that.
I love your hair. Who styled it?
The hairs on your nose have grown.
He has three long hairs on his chin.
“Earplug” is singular; “earplugs” is plural.
I lost one earplug.
My new earplugs are much more effective.
So if someone says “You have beautifull hair” so I can reply ,I make them look good ( I can use “THEM” right to refer them as plural tough the person just syas “hair”)