New health warning: temperatures reach 30 °C this week

A heat warning has been issued for parts of England, with temperatures expected to reach 30 °C (86 °F) on Friday.

The warning will apply from 17:00 (BST) on 18 July in London, the East Midlands, the South East and the East of England.

Areas of the UK that have experienced heavy rainfall so far in July are now likely to become significantly drier and warmer, albeit only for a short time.

A band of rain will move across the UK from the west over the weekend, bringing showers and some thunderstorms. It will be cooler for everyone by Sunday.

This will be the first warm weather spell this month for most parts of the UK, but it is unlikely to be the start of a heatwave.

In order to speak of a heat wave, temperatures must be above official heatwave limit on at least three consecutive days.

In Greater London, this limit is 28 °C. In Scotland, Northern Ireland, Wales and most parts of northern and western England, it is 25 °C.

However, temperatures could set a new record for the hottest day of the year after 30.5°C was recorded in Wisley, Surrey, on June 26.

A yellow warning means that weather conditions may pose a risk to particularly vulnerable people.

The UK Health Security Agency (UKHSA) has issued yellow heat warnings for four areas of England from 17:00 BST on 18 July:

• Eastern Midlands
• East
• London
• South-East

The warnings will remain in effect until 20 July, 23:00.

July was wet and cool across much of the UK, with temperatures below or just above seasonal averages.

In some parts of the country, including Loftus in North Yorkshire and Northolt in London, rainfall in July was already twice the average.

However, rain was not everywhere. Some northern and western areas, including Castlederg in Northern Ireland and Machrihanish in western Scotland, were comparatively dry, recording only about 20 to 25 percent of the average July rainfall.

Northern Ireland is much drier compared to last July, the wettest July on record.

The cool and wet July across much of the country was due to the jet stream – fast-flowing winds high in the atmosphere – which was predominantly over or south of the UK.

Over the next few days the jet stream will move north – a cloud of hot air from North Africa and Spain will bring a few days of sunshine to some parts of the UK.

However, over the weekend, thunderstorms in the east will cause temperatures to drop back to average levels, with cooler temperatures across the UK until Sunday.

Expect some showers and longer periods of rain next week, especially in the north and west.