Based on sct by Ted Unangst. Calculates sunrise and sunset based on geo-pos lat/lon and sets the temperature accordingly. Can be left running, in which case transitions between tempratures. Transition logic is based on redshift.
Precompiled binaries are available.
$ sctd --latitude 53.3498 --longitude -6.2603$ sctd --resetExecuting sctd in .xinitrc is an easy way to start it with startx.