An extensive research program has been conducted at the University of Western Ontario (UWO), Canada, during the past decade focusing on the response of Transmission Line (TL) structures to High Intensity Wind (HIW) events in the form of tornadoes and downbursts. This research was triggered by many failure incidents of TLs that occurred in various Canadian provinces during HIW events and by the fact that 82% of TLfailures worldwide resulted from those events. This multi-disciplinary research program was conducted numerically using state-of-the-art techniques and experimentally at the recently established WindEEE dome facility, which represents the only wind test chamber in the world capable of simulating downbursts and tornados at a large scale. The paper summarizes the outcomes of various phases of this research program, which included computational fluid dynamic simulations, structure modelling, failure investigations, and the first aero-elastic testing of a multi-span TLsystem conducted at WindEEE under simulated downbursts. Load cases simulating the critical effect of downbursts and tornadoes on transmission line structures resulted from this research, providing the first detailed procedure to design TLstructures to resist HIW storms.