Last month was the hottest June on record for Northern Ireland and Wales, and the fourth-hottest for Scotland and England based on 24-hour mean temperatures, the Met Office said.

The average maximum daytime temperature of 19.9C (67.8F) was the joint second-hottest, tied with June 1976 and just behind the 20.6C of June 1940, according to provisional figures.

Parts of south-east and central southern England also experienced their driest June on record, with 6% of expected rainfall. Essex had 1.7mm of rainfall, Dorset 2mm and Middlesex 0.7mm, the Met Office said.

It was the fourth sunniest June for the UK overall. Scotland recorded its highest temperature, 33.2C in Motherwell on 28 June, breaking the 32.9C set in August 2003 at Greycrook in the Borders.

While most of the UK is expected to enjoy more sunshine, thunderstorms and heavy rainfall were predicted for some parts of England. Heavy showers could hit parts of Devon and Cornwall on Monday with a chance of torrential downpours, the Met Office meteorologist Becky Mitchell said.

Elsewhere, temperatures were forecast to reach the mid-20s, with a maximum of about 30C possible in southern areas, meaning tennis lovers should see plenty of action as the Wimbledon championships begin.

The Met Office issued a weather warning for thunderstorms on Sunday after heavy rain in parts of southern England, but no warnings were in place on Monday.

Mitchell said: “There’s a lot of sunshine on offer, a bright and warm start to the day. Perhaps one or two showers affecting some central areas and stretching down towards the south-east as well, but they are very isolated.

People enjoying the hot weather on the banks of the river Thames in Putney, south-west London. Photograph: Amer Ghazzal/Rex/Shutterstock

“Later into the afternoon though, towards Devon and Cornwall, we will start to see a few heavy showers bubbling up. Some of these could be thundery and locally some torrential downpours too. But otherwise it’s a dry day on the cards, a little bit more in the way of cloud for the north-east.”

Any showers in the south-west are expected to clear by the evening, she said.

Ladbrokes has the UK at 4-6 to hit 35C this week.

Of the rest of the week, Mitchell said: “High pressure is largely in charge, we’ll see a lot more in the way of dry weather. Strong sunshine does mean temperatures will regularly get into the mid to high 20s for quite a few spots across the UK.

“This does mean that though there is a risk of thundery showers, they’ll be very hit and miss I think most places this week will stay largely dry.”