The impact of snowfall on THz channel performance is theoretically modeled and comprehensively measured for a 21m 140 GHz path and an 11m 270 GHz path. Bit error rate (BER) and path defects such as power loss and multipath effects were methodically recorded for variations in snowfall rate, carrier frequency, temperature and relative humidity and compared to theoretical predictions. Notable observations in this article include the presence of rapid power fluctuations and an absence of multipath effects. Insights from the modeling and measurements can be applied to protocol stack design and network planning to optimize channel performance and better accommodate environmental effects.