A local coffee roaster with a coffee shop offered cold brew a few summers ago, one of those when it was really hot. They stopped because it was too much work.

I drank it like whisk[e]y - in a similar glass and on ice (okay okay, ice and whiskey may not be a valid combination for everybody, but let's not get distracted, I used the image only for illustration). It was much more concentrated than normal coffee, and it tasted great! Very different from usual coffee and espresso. It also was a perfect drink during those hot summer weeks. I deeply regretted the apparent incompatibility of the commercial needs of the shop with this drink.

Going by the taste I experienced, and since they are a small roaster they always have new types of beans so I had several very different ones, I see no reason to heat this even if you don't drink it in a hot summer.

EDIT: [German] Looks like they sell it in bottles prepared in batches from their main store now, instead of day (night) in small daily batches: https://www.facebook.com/roesttrommel/photos/a.1510286749418... -- They write "Schmeckt am besten eisgekühlt." which translates to "Tastes best ice cold."