“So many people have said to me, look what’s happened since you started doing the weather,” says geography-teacher-turned-part-time-meteorologist Erin Roberts. “But it’s just the British obsession with whether it’s going to rain.”

As Ms Roberts returns to a new term at Ysgol Gyfun Cwm Rhymni in Bargoed, Caerphilly, the quizzical looks from pupils have begun. This summer saw the 29-year-old join the four-strong weather team on S4C. She will detail the warm fronts and scattered showers several weekends a term and during school holidays.

“If you ask the children I teach, they’ll tell you I do tend to harp on about the weather,” she says. Meteorology has been a fascination since childhood. She wrote to S4C on spec a couple of years ago, and a job came up this summer.

S4C viewers will quickly learn that teachers are never off duty. “I try to get a little bit of explanation in,” Erin says. “I don’t just say today it’s going to be raining - I try to explain in a simple way why it’s happening.”

The job involves constant contact with the government Meteorological Office, which provides the forecasts that Erin writes up into bulletins and, of course, translates into Welsh. Pupils can expect to explore how Hurricane Charley, having devastated the Florida coastline, went on to dump a load of rain over Wales.

Headteacher Hefin Mathias says: “It’s an interesting twist for Erin’s career. If the weather improves, the comments might be quite favourable.”

And you never know what is around the corner. “I’ve just had a phone call from Radio Wales,” she says. “They want me to explain why it’s raining fish in Powys.”