On the basis of two case studies, we searched the scientific literature to see if there was a connection between dehydration, extremely hot weather and the occurrence of neuroleptic malignant syndrome and if there were other risk factors for the development of neuroleptic malignant syndrome. Extremely hot weather, somatic comorbidity, the presence of catatonic symptoms and comedication (especially lithium and some antidepressants) are all risk factors for the development of neuroleptic malignant syndrome. Dehydration increases the existing risk.