Sydney was treated to an unusually vivid sunset on Monday night, after smoke from hazard reduction burns around the city timed perfectly with ideal weather conditions.

Pink, purple, red and gold were streaked across the sky, and soon across social media, as photos of the spectacle were posted to Facebook and Twitter.

Rob Sharpe, a meteorologist with Fairfax Media-owned Weatherzone, said the "very vivid" sunset brought "amazing colours" across the sky in much of Sydney.

"That was primarily due to the fact that we've got this low pressure trough that's now moved off the coast," Mr Sharpe said.