mildness, clemency -- (good weather with comfortable temperatures)
gentleness, softness, mildness -- (acting in a manner that is gentle and mild and even-tempered; "his fingers have learned gentleness"; "suddenly her gigantic power melted into softness for the baby"; "even in the pulpit there are moments when mildness of manner is not enough")
lenience, leniency, mildness, lenity -- (mercifulness as a consequence of being lenient or tolerant)