I just returned from my third round trip between Yucatán and Alaska in about seven months. I used to really notice the temperature transitions on these kinds of trips, but anymore the big changes don't bother me.
There was a time when I could not stand heat. I remember traveling from Alaska to warm climes and feeling as if I was going to die when the thermometer got above 85 degrees Fahrenheit (29C). When we moved to Miami and lived there for several years during my youth the air conditioning at home was always set at 68 degrees (20C). There were seasons when we hated going outside. When you opened the door, it felt as if someone walloped you in the face with a steaming hot, wet towel. We ran to the car, turned the AC on high, and battled over who got to sit by the air outlets.
Of the many reasons I moved to Yucatán, one was not that I wanted to live in extreme heat, but rather that I did not want to live so much in cold. There are milder climates nearer my ideal in other parts of Mexico, but I love Yucatán and so have learned to live with the weather. It's a good bit hotter here most of the time than in Miami. I have lived here for years without air conditioning and it's fine this way.
One thing I know now is that we felt uncomfortable in Miami because we kept the house so cool we never acclimated. If we had managed to get accustomed to a warmer inside temperature, the transitions to outdoors would not have seemed so extreme. We would have achieved better results dealing with the heat had we decided to live more with it.
Living with the heat is the answer to the problem. In Mérida I know people who love the heat, and I have come to believe that attitude can go a long way toward making heat bearable. A Yucatecan friend of mine embraces the heat and comments to me that he loves the feel of perspiration on his skin. Appreciating the energy that makes life on earth possible and finding ways to stop fighting it makes a lot of sense to me philosophically and environmentally. Deciding that the heat is not going to be a big problem, and then taking steps to minimize its impact goes a long way to making life in the tropics comfortable and pleasant.
Airflow and shade are very important. Living spaces with cross ventilation are more comfortable in hot weather, and high ceilings give heat and humidity a place to go above head level. One of the reasons the old colonial houses in Mérida are so popular with foreigners moving here is that they employ these types of design features to keep inhabitants cool. Fans are a huge help. I installed large-bladed ceiling fans in every room of my house and make liberal use of them, supplemented by floor fans in bedrooms. Once you live in a place for a while, you learn when to open and close which windows and doors in order to take advantage of breezes, keep sun out and the cool in. My routine of opening and closing parts of the house depending upon the time of day and weather keeps the house comfortable much of the time.
Clothing is important, as well, and besides using natural, breathable fabrics and loose garments I have only one rule: wear as little as possible. This is most easily done in the privacy of one's home and at the beach.
I can take a lot more heat when I am not working under pressure, or can pace myself and do things on my own schedule. Scheduling activities around the weather is probably the oldest way of dealing with heat. The siesta is maybe the best known of these strategies. I regularly take a siesta, planning work and energetic activities for early in the day and late in the evening, and reserve the heat of the afternoon for quiet activity or resting. Throughout much of Mexico, businesses and offices close or reduce staff in the afternoons so most employees can take a long, two-to-three hour break for lunch and a rest during the heat of the day. They then reopen late in the afternoon and keep their doors open into the evening. Evening meals are sometimes eaten as late as 9:00 or 10:00PM, when a lot of the day's heat has dissipated. In old urban neighborhoods, chairs are put out on the patio or sidewalk, doors and windows are thrown open, and families enjoy the night breeze and socialize with neighbors. As Mexico modernizes these practices are seen less, but they are still common, especially in the warmer parts of the country.
Generally I prefer to be hot in the outdoors rather than in an enclosed area, so I have open-air living spaces, and I use them. Trees rather than a roof provide shade, and shrubs and plants in place of cement surfaces keep temperatures down. A swimming pool, outdoor tub, sprinkler or shower -- anything that allows you to cover your body in cooling water from time to time -- provides instant relief in the heat. I take a quick dip or lounge in my backyard pool three or four times a day in hot weather. After the sun has gone down, rooftops provide access to breezes. Many homes in this area have rooftop terraces for evening relaxing and entertaining. While enjoying the cool of my rooftop I have a 360-degree view the city, stars, storm fronts and lightning passing in the distance, and observe owls and bats hunting in the night.
I started out living here without air conditioning because it didn't fit my budget. In renovating my house I was faced with a choice. I had enough money left to put air conditioning in the house or build the pool. I chose to have a pool and to worry about the AC later. I wired and plumbed the place for AC units, but after five years still have not put them in. Now I suspect I never will. Not using AC saves a lot of money and energy and lowers my impact on the environment. I have come to the conclusion that I don't need it. It's simpler this way and I live comfortably, so why bother?