When I was the senior court reporter for 2nd Infantry Division at Camp Casey, Korea, the courtroom was a Quonset hut at the top of the hill near the Division HQ. The heating and AC controls were in my office. In the winter, when the panel was deliberating, if it looked like they were taking up residence in the jury room, I would turn the heat off to that part of the building. In the summer, I would turn off the AC (I had windows and the jury deliberation room did not).
You'd be surprised at how quickly a jury can reach a judgment in their deliberations when the temperature outside is below zero.