Posted: 20/08/2013 at 17:52
It's best to forget about temps, per se, and just water when required, which means monitoring. They will need more water in warmer weather, obviously, but the mix should never be permanently damp. It has to be allowed to dry out.
I've got a spare Cherokee Purple plant - grown from a cutting - in a container on the terrace purely to save seeds from this year. The pot is smaller than 25L. It's in full sun for most of the day and the temps have been mid- to high-30s. I don't necessarily water it every day. I don't leave it bone dry for two or three days but I let it dry out.