In the US, September 1 marks the beginning of the Labor Day Holiday. While this is not a day of reverence as many holidays are, Labor Day marks the "official" end of summer and the beginning of fall. Daytime high temperatures begin to show signs of dropping off from the sweltering heat of the summertime. Nighttime temperatures drop such that people begin sleeping with their windows open and their air conditioning off. Harvesting of crops will begin in many areas, and the time of sunset in many southern locations has dropped by 1 hour at the end of the day (8:30pm local back to 7:30pm local).
In other words Labor Day it's a sign that the US winter heating season will soon be upon us and we must prepare - measure, insulate, conserve and take measures to blunt the energy and cost impact of the impending winter weather. You may want to wait another couple months before installing that temporary plastic wrap on your windows to gain your cold weather insulating layer, but it's definitely time to start measuring, planning, and assembling the components you need for your home energy projects.
Ironically, the months of September through November may be the months of lowest energy usage for many of you in the temperate zones of the US. Your air conditioning stays off, you don't need heat yet, and there's enough daylight that home lighting isn't a factor. This lulls us into a false sense of energy efficiency, and we don't get our conservation projects done until it's bitterly cold outside and we've already gotten that terrible power or gas bill.
Prepare, friends. Prepare now. Start measuring now. If you have been considering buying or making energy measurement equipment, do so now and get it installed as quickly as possible. This time represents a valuable time of "baseline data" you can use as you go into the winter months to determine how well you are doing and what you can do to more effectively save energy and money during the deeply cold months of winter.