The arctic blast that brought record low temperatures to many parts of the United States this week appeared to be loosening its grip on Wednesday, with meteorologists promising a far-reaching thaw by the weekend, reports the Guardian. But experts warned that many areas would remain below freezing on Wednesday despite the warm-up, and that travel delays from cancelled flights and rail disruptions caused by the so-called polar vortex could still be expected.

Pic: The frozen Niagra Falls that's doing the round on Twitter. The authenticity of this photograph has not been established.