Looking for a holiday destination this summer? Think you need some sun? Here are some cities that are going to be too hot to visit. 1, Seville, Spain. Reaching average summer temperatures of 90°F–92°F, this Andalusian gem is the hottest city in Spain. 2, Athens, Greece. This Greek capital city has unbearable summer temperatures soaring above 95°F regularly and has heat waves sweeping over often. 3 , Marrakech, Morocco. Marrakech becomes unbearably hot from June to August, with temperatures hitting well over 100°F. 4, Dubai, UAE. With temperatures around 105°F from June to September and the extreme humidity, Dubai is a must-avoid destination in summer. 5, Phoenix, Arizona. Phoenix, one of the hottest cities in the US, regularly exceeds 100°F, often hitting 110°F.