Set in

That was the point at which the rot set in.

[...] but rain set in, driven by a furious westerly gale, [...].

By the afternoon it seemed as if the storm had passed and that frost was setting in; but in the evening the wind rose to gale force, bringing telegraph poles down like skittles and tangling power and telephone lines.

Work on anti-frost precautions on diesel locomotives is to be speeded up to ensure that most if not all locomotives have been dealt with before the winter sets in.