EzekielRaiden
Follower of the Way
Well, the idea with "languid" is that the sun lingers a long time in the sky on summer days...Actually, that's nearly better than my actual answer!
"A river" and potentially, if a named river has played a role in the game narrative, that specific river.
Also reiterating my ninja edit, I might suggest 'balmy' over languid. Languid is a kind or degree of motion, rather than a temperature.
which is when icicles can't form (or if you somehow had one, it would quickly melt and disappear). Felt something like "balmy" (which I did consider!) would be too much of a giveaway for the cold.