The longest day of the year for the North hemisphere has relation with the summer solstice, when the Sun reaches its maximum height. More sunlight could be associated with less energy consumption and that's possible, although some locations even raise it due to measures in the task of acclimatisation.
When the heat comes the quantity of corporal grease obviously interferes with the perceived sensation. However, a person who makes partially intensive sports does stand better in presence of high temperatures. It's recommended to not have excess grease and make sport frequently; in fact, some individuals are between the only species that still conserve the grease without the intention of being a protection for cold environments or as a nutritional resource. Birds for instance, usually get grease for the winter but it's rare to see them in that shape in the hot months of the year!
An appropriate policy for not consuming an excess quantity of energy or having problems due to the extreme temperatures appears in the so-called heat isolation. As the morning comes with fresh air, in a usual home scenario, it should be used to decrease the overall temperature opening windows, doors or whatever mechanism for letting the airflow. Once it's done, the air must be “trapped” with the inverse operation. As a reinforcement to avoid re-heating the blinds should remain mostly closed during the day avoiding direct sunlight.
With this simple technique multiple people completely avoid the use of machines to control the temperature and also all inherent problems principally air pollution and resource exhaustion as electricity comes from carbon sources in a considerably high percentage. In some locations the act of consuming electricity is an act that helps in the environmental degradation that sooner or later causes problems to everyone.