My definition: torture is the use of any measures on a detainee which are for the purpose of forcing them to reveal information against their free will not to. I'm against it in all reasonable cases (if it could very likely prevent a nuclear attack? Well, we can talk, but that's unlikely to ever happen).
Let's run through a few examples for my test.
Allowed are measures designed to persuade the person to talk: ideological/propaganda, rewards, befriending the person, long hours of interviews but not to the point aimed at physical/mental inability to resist.
Not allowed: waterboarding aimed at overcoming the ability not to answer, heat/cold/other discomfort to the extremes aimed at overcoming the ability not to answer, sleep deprivation aimed at overcoming the ability not to answer, etc.
Allowed: heat, cold, sleep deprivation, hunger, noise, and other suffering *for legitimate reasons* to a degree appropriate for the fact that the person is in custody, not a hotel, but not aimed at overcoming their ability to not answer things.
I think that my definition captures the issue of torture very well...
"Your honor, my client was tortured by the use of thumb screws." The interrogators would have little defense for such a device.
"Your honor, my client was tortured by not being able to sleep for 48 hours from the noise." The interrogators: "He was detained in a cell where there was a battle going on for 48 hours - the noise was not aimed at causing him suffering to force him to talk, but was part of the situation of where he was taken into custody". Not guilty.
"Your honor, my client was subjected to 115 degree heat all day for days on end". The interrogators: "This happened while he was being held on the battlefield where he was captured until transferred to prison - everyone was suffering from 115 degree heat all day for days on end". Not guilty.
The bottom line is, if the measures are designed to force the person not to be able to keep quiet, from suffering - whether from pain, sleep deprivation, heat and cold, hunger, sexual abuse, etc., it's wrong to do to someone powerless in custody. The measures used which are reported to sometimes cause long-term psychological damage are far over the line IMO.
I can't answer the question the way PH asked it, because they aren't 'yes/no', topics, as described above. Heat/cold? Depends on the situation - was it used to force talking?