// BBC UK NEWS — CRONACA
UK set for coldest night of autumn so far
After a spell of unusually warm weather, temperatures across the UK are set to tumble with the coldest night of autumn so far arriving by midweek.
Wednesday night will bring the first frost of the season to some places, as colder air arrives from the Arctic.
In some areas, minimum temperatures could be just a degree or two above freezing by dawn on Thursday.
Along with the plummeting temperatures, some much-needed rainfall is on the way for England and Wales.
A southerly shift in the jet stream will allow colder air to flood across the country through the middle of the week
So far this autumn, the jet stream - which determines what sort of air mass affects the UK - has been sitting to the north.
This has allowed mild south or south-westerly winds to flow, particularly across the southern half of the British Isles.
This week, however, the jet stream will start to sink further south, allowing the winds to turn more northerly and introduce a colder air mass.
While it will feel significantly colder compared to recent weeks, especially in the south, temperatures will actually be near normal for the time of year or perhaps just a little below.
Afternoon highs on Wednesday will be around 12C to 14C in Northern Ireland and Scotland and 14C to 16C in England and Wales.