What uncountable nouns can be preceded by an adjective and the article in front of them can be used as a? For example, if there is a heavy rain, why is there no a hot water?

What uncountable nouns can be preceded by an adjective and the article in front of them can be used as a? For example, if there is a heavy rain, why is there no a hot water?

That's not what I said
Countable nouns can add a, but uncountable nouns can't
A is added before rain because rain can be counted here
Water is uncountable, so it's not added