Third heatwave for parts of the UK is on the way as 30C temperatures are forecast

Another heatwave is likely to be declared in parts of the UK as temperatures rise over the weekend.

On Sunday, temperatures could hit 30C in southern England as an area of high pressure moves in from the Azores.

But with the wind coming from a westerly direction it could mean the extreme temperatures experienced during the second half of June may be avoided initially.

Last month was the warmest June on record for England, and the second warmest for the UK as a whole, according to provisional data from the Met Office.

A heatwave is declared in the UK once daytime temperatures meet certain thresholds, which vary across different regions.

In London and the south-east, for example, three consecutive days of 28C are needed, while in northern Britain it is 25C.

Much of the UK will remain below these criteria through the rest of this week. On Friday it is possible temperatures could just nudge to 28C within Greater London and the Home Counties.

On Sunday, with top temperatures forecast to hit 30C, this would be the earliest day a heatwave could be declared in a few spots in England.

It will get progressively warmer next week across much of the country, with hot air establishing itself across southern Britain.

Highs are expected to approach or exceed 30C on most days, with slight day-to-day variations in location and temperature.

Later in the week, however, it is possible that southerly winds could briefly return lifting temperatures a little higher, but there is a lot of uncertainty around this.

The UK Health Security Agency has issued yellow heat health alerts for the East Midlands, East of England, London, south-east and south-west from Saturday, warning that there is a greater risk to life for vulnerable people as a result of the temperatures.

However, unlike the last heatwave, the air is expected to be less humid, at least initially. So despite the high temperatures, it may feel a little more comfortable.

In northern areas, temperatures are not forecast to reach heatwave levels quite so soon - if at all.

The high pressure may be a little further south, allowing fresher Atlantic air and perhaps scattered rain clouds to filter into Northern Ireland, Scotland and northern England due to their closer proximity to the jet stream.

Temperatures in Belfast, Liverpool and Glasgow are likely to level off at a pleasant 20 to 24C.