Background: Heat related illness can be avoided; it may also be present in a milder form to a life threatening condition. Objectives: To explore the pattern of KAP towards HRIs among the subjects in Jeddah city. Method: It was a cross-sectional study of 378 subjects, who gave their responses through an online Google form. Data were analyzed using SPSS software version 23. The level of significance was 0.05%. Results: 18.2% of the subjects suffered from HRls, and 49% never received health education about HRIs. Increased KAP score was associated with increased age (b= 0.177, p<0.000), more encountered in the females (b= -2.25, p <0.000), in those who owned air conditioning (b = 5.3, p < 0.024), in the smokers (b= 1.77, p<0.35), and in those who received health education about HRIs (b=2.327, p< 0.000). Conclusions: The subjects' awareness of the prevention of HRIs needs to be strengthened.