The final days of September will bring an unusual combination of warmth, strong winds, large waves and spells of rain, before conditions gradually settle during the opening days of October.
High pressure will provide a largely fine start to the week. However, low pressure developing over the Atlantic will become the dominant influence through Tuesday and Wednesday, bringing strengthening winds and a band of heavy rain across the UK. High pressure is then expected to build again later in the week, particularly across southern areas.
Unseasonably warm on Tuesday
A warm front moving northwards early on Tuesday will bring plenty of cloud and some showery rain across England and Wales. The outbreaks will be rather hit and miss, meaning many places will remain dry despite the generally cloudy start.
The cloud should begin to break across southern England during the afternoon, allowing sunny spells to develop. At the same time, strengthening southerly winds will draw unusually warm air across much of England and Wales.
Temperatures could reach 24 or 25°C in parts of southern Britain, with 26 or perhaps 27°C possible around London. This would be notably warm for the end of September. Further north, temperatures will be lower but should still be close to, or slightly above, the seasonal average.
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Wind and rain arriving from the west
The weather will become increasingly unsettled through Tuesday evening and overnight as a cold front approaches from the west. Rain will spread into western areas, becoming heavy in places, while winds strengthen widely.
It will also be an exceptionally mild night for the time of year. Many areas will begin Wednesday with temperatures still in the mid or high teens, and parts of eastern England could remain even warmer.
Wednesday morning will be wet for many as the cold front moves slowly eastwards, bringing some heavy rain. Brighter conditions will follow from the west, although these will be accompanied by a number of showers.
Tuesday, Tuesday night and Wednesday will also bring a particularly blustery spell. Despite above-average temperatures, the strength of the wind may make it feel cooler. Large waves are also expected around some western coasts as the deep area of low pressure passes to the northwest.
Gradually calming down
The main band of rain should clear by the end of Wednesday as the low-pressure system moves further away. Conditions will begin to calm, although high pressure will initially be slow to establish itself fully.
Thursday is therefore likely to bring further showers. These may initially affect eastern areas, while scattered showers develop across Wales and feed into the Western Isles on a brisk wind.
Temperatures will return closer to the early-October average, although eastern England could still reach 20 or 21°C where sunny spells develop.
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High pressure builds
High pressure is expected to become more established across southeastern parts of the UK from Thursday night. Meanwhile, another weather front will attempt to move into Scotland and Northern Ireland before extending towards Wales.
This will bring more cloud, brisk winds and some outbreaks of rain to northern and western areas. However, the front may struggle to make much progress against the area of high pressure, allowing eastern England to remain largely dry.
By Saturday, high pressure looks likely to win out across much of the country, pushing the weather fronts away and bringing a dry day for many. Cloud and rain may still approach the far northwest, but current indications suggest that much of the UK will begin October’s first weekend with quieter and more settled weather.
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