The UK heatwave is expected to continue this week, with new 2021 temperature records expected on Sunday.

The Met Office said the mercury could hit 32C (89.6F) in London on Sunday, making it the hottest day of 2021 so far in the UK – although it could be beaten again in coming days.

Northern Ireland experienced its hottest day ever on Saturday afternoon with 31.2C (88.16F) recorded in Ballywatticock, in County Down, beating the previous highest temperature of 30.8C (87.44F), which was reached on July 12 1983 and June 30 1976.

All four nations recorded their highest temperature for the year so far on Saturday, with 30.3C (86.54F) recorded in Coton In The Elms, Derbyshire, 29.6C (85.28F) reached in Usk, Monmouthshire, Wales and 28.2C (82.76F) in Threave, in the Dumfries and Galloway region of Scotland.

However, those highs are expected to be beaten on Sunday in Wales and England with temperatures predicted to reach 30C (86F) in Cardiff and 32C in London.

A Met Office spokesperson said: “We are expecting temperatures to continue on the high side right through until Thursday, although the day-to-day detail will change and there is a tendency for the highest maximum temperatures to migrate west.

“So, we are expecting Monday and Tuesday for the maximum temperatures to be in the South West and in South Wales, and then later in the week temperatures climbing across Northern Ireland and the North West.”

Temperatures are not expected to beat yearly records on Sunday in Northern Ireland or Scotland with highest estimates at 28C (82.4F) in Belfast, Northern Ireland, and 22C (71.6F) in Threave, Scotland.

Sunday’s high temperatures mark the beginning of an official heatwave across the UK, as in London and the South East, temperatures must exceed 28C for at least three days to record a heatwave, and Sunday is the third day.

This requirement drops to 27C (80.6F) in the Midlands and 26C (78.8F) in the South West, which has also been met on Sunday and is also expected to continue throughout the week.

The Met Office is working with Public Health England to ensure that people stay safe in the hot conditions, urging the public to stay hydrated, wear sunscreen and assist anyone who is more vulnerable to the heat.