Scorchio! The Fast Show’s persistently sunny forecasts from Caroline Aherne have got nothing on the flaming reports delivered by Julia McDermott as Stacey, a California weather girl in meltdown. One of Stacey’s regular bulletins careens into an apocalyptic, scorched-earth stream of consciousness, raging against reckless consumerism and environmental ignorance, in this tragi-satirical monologue written by Brian Watkins. And it is a fast show, tautly directed by Tyne Rafaeli for Francesca Moody Productions and performed in a caffeinated rush by the captivating McDermott. “I am your rise and shine,” she insists – voice perky, cheeks rosy, skirt hot pink – but a numbing nihilistic despair is barely concealed. Filming a segment on a wildfire, she strikes a pose for the cameras but utters “I can’t hold this smile much longer” – an alert not just about her personal breakdown but the planet’s. This emotional weather report covers encounters with Stacey’s TV colleagues, a tech bro and, most pertinently, her estranged mother, although that relationship is not drawn with the depth it requires. You suspect that Watkins, who created the sci-fi western series Outer Range, would benefit from a bigger canvas here. Instead, Weather Girl often resembles a series of sketches, narrated in character-comedy mode, except Stacey’s cheap-prosecco-in-my-travel-mug routines are less well wrought than the play’s vividly unsettling atmosphere. Watkins writes of 4am smelling like evil, the “devil’s breath” of California and a landscape razed for strip malls, selling plastic tat that will outlive us all. Stacey’s continuous sense of disconnect is well done, and a deft lighting design intermittently plunges from cheery TV artificiality into nihilistic darkness. A link is drawn between the practice of water divining and the need for us to find our own source of inner purity to tackle the climate emergency. That, too, is not quite fully formed, but there is no doubting the hurricane force of McDermott as, like a latter-day Howard Beale from Network, she sees the soaring weather forecast and refuses to take it any more. The question, the play asks, is will we join her cry? At Summerhall, Edinburgh, until 26 August All our Edinburgh festival reviews