[2] Born and raised in Burlington, Ontario, Harmer gained her first exposure to the musical lifestyle as a teenager, when her older sister started taking her to Tragically Hip concerts.

[5] After leaving The Saddletramps, Harmer put together a band of her own with several Kingston, Ontario musicians, and chose the name Weeping Tile.

[9][10] A poppier, more laid-back effort than her work with Weeping Tile, You Were Here was a commercial success, and led to the hit singles "Basement Apartment" and "Don't Get Your Back Up".

[16] On August 19, 2016, Harmer and Jim Creeggan appeared on CBC Radio's Q to perform a live cover of The Tragically Hip's "Morning Moon".

[23] To support the organization, she and her acoustic band embarked on a tour of the escarpment, hiking the Bruce Trail and performing at theatres and community halls in towns along the way.

Harmer also coauthored a book about the campaign, The Last Stand: A Journey Through the Ancient Cliff-Face Forest of the Niagara Escarpment, which was published in 2007.

Harmer has performed and canvassed in support of the NDP and politician Marilyn Churley, who also promoted the protection of the Niagara Escarpment.

On March 24, 2018, she joined the demonstration at Kinder Morgan's Burnaby Terminal to protest against the expansion of the Trans Mountain pipeline.

Her niece Georgia Harmer, the daughter of Sarah's sister Mary with their former Weeping Tile bandmate Gord Tough, is a singer-songwriter whose debut album Stay in Touch was released in April 2022 on Arts & Crafts Productions.

[26] In 2007, Harmer also reunited with Weeping Tile to record a song, "Public Square", for the Rheostatics tribute album The Secret Sessions.