Thursday will see a stark split in Britain's weather. Warm air drawn north by a deep area of low pressure near Iceland will lift afternoon highs in south-eastern parts of England to between 19C and 23C (66-73F), about 5-8C (9-14F) above the seasonal norm. Sunny spells will make it feel unseasonably warm for late October.
Further north and west, the picture is different. Scotland and Northern Ireland will see temperatures closer to the typical autumn range, with a weather front bringing outbreaks of rain that are expected to edge slowly southwards through the day, leaving a soggy afternoon for northern England, Wales and parts of south-west England.
Behind this front, chillier air will spread to all parts of the country over the weekend. Though sunshine is still expected, temperatures will drop to a more seasonable feel. Frost and patchy fog are likely to develop in some locations as the colder air settles in.