The batches of this (a great porter) that I have made were chilled to <70F, and put in our basement, which runs in the low '60s for most of the year. Last Spring was the most recent batch, and it was unusually warm weather, so I'd say 63-65F.
“Malt does more than Milton can / To justify God’s ways to man”
-A. E. Housman (1859–1936). A Shropshire Lad , 1896.