Green’s Dictionary of Slang

weather gig n.

the vagina.

c.1707		‘Bonny Peggy Ramsey’ in Farmer Merry Songs and Ballads (1897) II 151: And square is her Wethergig made like a Mill [...] Bonny Peggy Ramsey she gives weel her Mill.
1890–1904		Farmer & Henley Sl. and Its Analogues.
c.1904		A. Crowley Snowdrops from a Curate’s Garden 34: The pressure of her lousy but expert weather-gig gave me excruciating agony: for it was impossible even to work in order to produce ejaculation.