Victor Fleming, USA, 1939
This film is clearly set in an imaginary register, creating a totally artificial, fantasy world, even if it contains elements borrowed from the real world. This means that there’s no recourse, whatsoever, to realism in the studio’s depiction of this cinematic tornado. The wind comes from a wind machine (cf Le Déjeuner sur l’herbe). Technicians throw the occasional tumbleweed into the picture, which are blown across the screen. The tornado itself is clearly an animation, superimposed onto pre-recorded shots and sequences.
The elements of the set that move in the storm were carefully prepared so as not to cause any harm to the actors, such as the door to the house, which flies off the minute that Dorothy touches it, or her bedroom window which comes loose and hits her on the head.
When the house flies away, the image becomes totally unreal and the character views their own dream as if on a screen, framed by the space the window left in her bedroom. The world looses all stability and no longer obeys the laws of perspective nor weight. (cf The Gold Rush)