Onstage, clouds can convey many things about the action of a play. Fluffy white clouds show happiness, and looming trouble is foreshadowed as grey and black clouds gather in the sky. Making clouds as stage props can be extremely simple, with the use of a few materials and a little bit of creativity.
Cut cardboard in cartoon-like cloud shapes. Paint them white with slight overlay of iridescence or cover with bunched up white silk or a fluffy polyester white plush toy stuffing. Hang onstage, peeking from beneath the upper curtain or work into the backdrop.
Measure long swathes of sheer fabric in white, grey and/or black that can stretch comfortably across the length of the stage with some excess on either side. Have stagehands stationed in the wings on either side of the stage wave and flutter one or more swathes of fabric. Work with the lighting and sound designers to create special effects that help bring these ethereal clouds to life.
Project images of clouds onto the backdrop. Work with your lighting and sound designers to create a digital film of the type of weather you want onstage. Add sound effects like birds singing, wind blowing or thunder.