UK weather: Britain forecast to bask in balmy 21C as mercury continues to rise this week

Warm 21C weather will be making a comeback this week, according to new forecast maps, as a change in pressure systems banishes the cold air and marks a return to summer-like temperatures

Britain is set to enjoy above-average temperatures of 21C very soon as weather conditions heat up after a chilly start to week.

Many parts of the country have been waking up to frost and cool autumnal weather in recent days, with the mercury diving to -2C overnight in some northern regions on Monday. However, a change in pressure systems means the colder air is now heading out towards Scandinavia, and is being replaced by a new warmer front arriving from the Mediterranean. The change in conditions will be obvious to Brits pretty quickly, with a move to higher temperatures expected as early as this morning.

Maximum daytime highs will register in the high teens across many areas on Tuesday, and on Wednesday, London and parts of the southeast will bathe in summer-like temperatures of 21C. That's five degrees above the average daytime maximum of 16C.

Discussing the change in the weather, Alex Deakin from the Met Office said in a new bulletin: "Yes, it's mild on Tuesday, but it'll be warmer still going into Wednesday. That warmer air will be wafting its way north - these weather fronts, though, are introducing moisture and outbreaks of rain. The overnight temperatures as we head into Wednesday are significantly above the average for the time of year, by three to six degrees, and in some places even higher than that."

He did warn however that higher temperatures do not guarantee widespread sunshine, and said that "pulses of rain" will be "tracking northwards" throughout the day. The east of Northern Ireland, Wales, northwest England and eastern Scotland would be appeared to be at risk of the heaviest downpours from early forecasts, he added.

Further ahead, the weather is likely to start looking much more like autumn, including colder spells and frosty mornings. The Met Office's long-range forecast for Saturday 19 October to Monday 28 October reads: "This period is likely to start changeable and often unsettled but relatively mild, with rain or showers for most places. There is potential for a deep area of low pressure to develop to the west or northwest of the UK early in this period, bringing a spell of very strong winds and heavy rain, especially to parts of the west and north.

"Towards the latter part of October, there are signs that whilst northwestern areas may continue to feel the influence of areas of low pressure, further south pressure is expected to build, bringing more in the way of fine, settled conditions. With this comes an increasing chance of overnight frost and fog, with the latter perhaps persisting well into the day in some areas."

UK weather forecast:

Cold in the north tonight, milder in the south.

Tuesday:

Mainly dry, though fairly cloudy. Northern Scotland seeing the best of the sunshine. Patchy drizzle under areas of thicker cloud. Some heavier rain in the west and southwest later. Breezy.

Outlook for Wednesday to Friday:

Unsettled on Wednesday with some heavy rain at times. Winds slowly easing. Drier and brighter on Thursday. Turning wet and windy from the west on Friday. Milder than of late.