As Britons bask in the late summer spell that has enveloped much of the country, forecasters are warning that wet and windy conditions are soon set to take over.

The Met Office has issued severe weather warnings for rain on Friday (16 September) and Saturday and temperatures are likely to drop by at least 10C across the country by the end of the week. The warning comes one day after the hottest day of the year was recorded on Tuesday, with highs of 34.4C.

Temperatures remained high in the UK on Wednesday, with highs of 28C expected on Thursday as well. However, by Saturday, maximum temperatures in the south-east will have dropped to 18C and will be accompanied by torrential downpours in England and Wales. Forecasters fear that as much as 30-40mm of rain could accumulate within one hour, with as much as 50mm within a few hours.

"Rain spreading from the west may turn locally very heavy and thundery from early Friday, with the risk of some torrential downpours very locally," a chief forecaster for the Met Office said. "While the vast majority will have much less than this, it could cause disruption, especially if heavier bursts coincide with urban areas."

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This could mark the end of the summer weather for the rest of the year. The final weeks of September are also set to bring showery conditions for many, with temperatures unlikely to rise once again.

"The most likely scenario is for changeable and often unsettled weather to continue through this period with most places seeing showers or longer spells of rain," a forecaster for the Met Office said. "As we move into October, there is an increasing risk of more widespread wet and windy weather across the UK."

However, there is a low chance that the middle of October could see some more settled conditions. While temperatures are expected to be near normal for the time of year and at times milder in the south-east, there is no indication that the UK will see heatwave conditions as seen this week.

Apart from being the hottest day of the year so far, Tuesday was also recorded as the warmest September day in 105 years. Thousands of Britons were out to enjoy the sun in the south-east and the hashtag "heatwave" was trending across the UK throughout the day.

Temperatures in London meant that the capital was warmer than some of the world's summer hotspots – including Barcelona, Miami and Rome. Despite the record-breaking day, weather experts have said that the warm temperatures are not unusual for this time of year.

A spokesperson for the Met Office told IBTimes UK: "At this time of year the seas around the UK are at their warmest and so provided we have a warm air mass over or near to the UK, this tends to prevent temperatures dipping too much."