Outdoor environmental conditions are major drivers for building heating and cooling loads. The author has been interested in meteorology for most of his life and has have learned much about climate data acquisition and reporting in real time. However, he wasn’t as familiar with how the normalized (for example, typical meteorological year or TMY) data sets are developed. But thanks to a recent project, he was able to explore that topic and learned some surprising things. In this column he shares some of those insights.