coldness has 7 distinct synonyms spread across 3 of its 3 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is hotness.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
the sensation produced by low temperatures
“he shivered from the cold”
a lack of affection or enthusiasm
“a distressing coldness of tone and manner”
the absence of heat
“the coldness made our breath visible”
Synonyms, antonyms and the broader and narrower relations for coldness come from Princeton University’s WordNet. Full sources and licences.