Many older antipsychotics, particularly phenothiazines (like chlorpromazine) are notorious for causing adverse phototoxic reactions to sunlight such as rashes and skin redness/pigmentation and inflammation, and also affect the bodies ability to regulate temperature and sweat (also affecting salt balance and hydration levels).

The whole temperature regulation system is based on a very complex homeostatic system that involves a number of neurological pathways that can be affected by a wide variety of psychiatric medications, particularly any that impact on serotonin levels, glutamate levels, cholinergic pathways, the autonomic nervous system in general etc - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3051412/