Typical Meteorological Year (TMY) represents a complete 12-month weather dataset constructed from actual historical monthly observations, selected to represent statistically typical conditions for a geographic location without unusual seasonal extremes. TMY datasets enable realistic annual energy modeling and building performance prediction compared to design-day peak conditions.
Development Methodology
TMY datasets are assembled by selecting the statistically most representative month from available historical records (typically 20-30 years) for each calendar month. Selection criteria evaluate monthly statistics including mean temperature, maximum and minimum temperatures, humidity, solar radiation, and wind speed. The resulting composite year avoids seasonal anomalies while maintaining realistic hourly variability, precipitation patterns, and solar radiation cycles. NREL’s TMY3 and TMY4 datasets represent the most widely used U.S. reference data.
Simulation and Design Applications
Annual energy modeling requires TMY data to predict building energy consumption, operational cost, and equipment performance across typical weather variation. Unlike design days (1-2 representative days annually), TMY data provides 365 diverse weather conditions, capturing how systems perform during shoulder seasons, partial-load conditions, and various occupancy patterns. TMY data includes realistic solar radiation profiles essential for photovoltaic and daylighting analysis, typically 5-10% more detailed than design day specifications.