Temperatures are set to increase on Thursday and Friday before potentially hitting 29C (84.2F) on Saturday ahead of the arrival of thundery conditions, the Met Office has said.

The humidity at night will also become "uncomfortable" as some areas will not get below 15C (59F) or 16C (60.8F), compared to about 3C (37.4) at the start of the week.

Click here for the latest forecast

Meteorologist at Sky News, Christopher England, said: "Temperatures over the weekend look set to reach 28-29C over parts of the south, 27C over central England and 26C for many other western parts, but could go a couple of degrees higher.

"Eastern coasts will be quite a bit cooler, with an onshore wind keeping top temperatures in the mid-teens on Saturday, but changes in wind direction mean it will turn warmer for many on Sunday, before an easterly wind returns next week.

"An official heatwave is possible in parts of the south and west, but cloud cover and occasional rain mean that the 'three days above the threshold' criterion may not be met.

"Top temperatures look like staying mostly above average for the next week, but it should turn a bit cooler thereafter."

Forecasters expect the highest temperatures on Saturday to be in areas north of London.

On Thursday, Storm Oscar, which is currently across the Canary Islands, will drive a warm plume of air towards the UK, causing temperatures to rise with southwest England and southwest Wales expected to enjoy the warmest weather.

From Friday, it will continue to get warmer but alongside a bigger risk of showers across southwest England.

The warmest temperature expected on Friday is 26C or 27C, most likely in central and southern England.

Read more on Sky News:
England 'not ready' to respond to extreme heatwaves this summer
How to sleep better during hot conditions

Showers expected to 'become heavy at times'

Simon Partridge, of the Met Office, said: "We continue with showers on Sunday and Monday and it will turn a little bit cooler again.

"Showers over the weekend will become heavy at times, and there's a risk of a bit of thunder.

"There will be 10-15mm of rain over the course of two to three hours, which is nothing too significant."

Heat warning for vulnerable groups

The UK Health Security Agency (UKHSA) has issued a yellow heat health alert - when the weather is likely to impact vulnerable groups such as those with underlying health conditions, or the elderly - for southern and central England for between 9am on Friday until 9am on Monday.

Dr Agostinho Sousa, of the UKHSA, said: "In the coming days we are likely to experience our first sustained period of hot weather of the year so far, so it's important that everyone ensures they keep hydrated and cool while enjoying the sun.

"Forecasted temperatures this week will primarily impact those over the age of 65 or those with pre-existing health conditions such as respiratory and cardiovascular diseases.

"If you have friends, family or neighbours who you know are more vulnerable to the effects of hot weather, it is important you check in on them and ensure they are aware of the forecasts and are following the necessary advice."

The hottest temperature in the UK so far this year was 25.1C (77.2F) in Porthmadog, Wales, on 30 May.