The populations in those areas used to be far lower, and temperatures were lower during the "Little Ice Age", which covers much of that period. People just put

The populations in those areas used to be far lower, and temperatures were lower during the "Little Ice Age", which covers much of that period. People just put up with it, or adopted appropriate traditions such as siestas during the hottest periods of the day. We also adapt to conditions remarkably quickly, and are physically capable of surviving far outside what we normally consider comfortable. When visiting the south, it's not uncommon to see people complaining of cold in 60F weather which is quite comfortable to northerners, who start to complain about heat past 70F. Building materials and styles of construction were different - before modern transportation and logistics, you couldn't build exclusively with wood in areas with no trees and few rivers to float barges, and insulation was accomplished through thicker walls. People used parasols, shawls, and other clothing to cover up and insulate their bodies rather than their entire surroundings. Swamp coolers have been known for thousands of years.