The Guardian LONDON, England, By Robyn Vinter —  Freezing temperatures could be about to blast the UK, putting an end to the unseasonably warm October, and heavy rainfall is expected in parts of England.

Frost is forecast in parts of the north of England and snowfall in the Scottish uplands, the Met Office has said, as the mercury plummets after the warmest October temperatures in five years were recorded at the start of the month.

Northern Ireland and parts of Scotland could reach as low as -3C (26.6F). The south of England and Wales could see about two inches of rain on Thursday and Friday, and the Met Office is warning of possible thunderstorms, flooding and travel delays.

Grahame Madge, a Met Office spokesperson, said: “On Wednesday night there may potentially be some frosts and much colder than average conditions, which might be a shock for northern parts of Britain because we’ve had this relatively warm air across most of the UK.

“There will be an increasing tendency towards cooler conditions, however in the southern parts of England and Wales we’ve got the prospect of heavy rain coming in. We’re saying there is a significant rain warning from 9pm on Thursday through to midnight on Friday, and we can expect 20 to 30mm in some places in a couple of hours. Even up to 50, 60 or possibly up to 70mm across the high ground of Wales.”

The rain will be followed by “much cooler conditions, six degrees below average”, Madge said. “Given the fact a few days ago we were talking about conditions six or so degrees above average, [this] will feel like a marked contrast.”