UK heat health alerts are in force across central and southern England as temperatures could reach 30°C on Friday, raising health risks for vulnerable people before cooler air and limited rain arrive over the weekend.

The yellow alerts, issued by the UK Health Security Agency, began at 09:00 BST on Friday and remain valid until 09:00 on Sunday. They cover the East Midlands, West Midlands, East of England, London, south-east England and south-west England.

The agency expects the heat to have minor effects on health and social care services, while warning of a greater risk to life among vulnerable groups. That includes older people, those with existing health conditions and anyone who may struggle to keep cool.

Where will temperatures be highest?

A recent north-westerly airflow will briefly ease across southern areas on Friday, allowing temperatures to rise sharply.

Central, southern and eastern England are forecast to reach 25°C to 28°C in many places, with a few locations potentially hitting 30°C. Parts of eastern Wales could also climb into the high 20s.

Elsewhere, temperatures are expected to remain warm but less intense:

  • Wales and northern England: generally 20°C to 25°C
  • Northern Ireland and Scotland: afternoon highs of 19°C to 23°C

Most of the UK will experience sunny spells. North-west Scotland is the main exception, with thicker cloud and patchy rain expected to arrive during Friday afternoon.

Fresher north-westerly winds should return over the weekend, gradually lowering temperatures. By Sunday afternoon, highs are expected to range from about 16°C in northern Scotland to 25°C in south-east England.

The change should end unusually persistent heatwave conditions at Usk in Monmouthshire and Exeter in Devon, where the threshold has been met for 19 consecutive days.

Will the weekend rain ease drought conditions?

High pressure is forecast to retreat westward, allowing weather fronts to move south-east across the UK and produce outbreaks of rain. Unfortunately, the areas most in need of sustained rainfall may receive very little. The weather remains unhelpfully selective.

Rainfall could be more substantial over higher ground in northern and western parts of the country. North-west Scotland may receive around 20mm, or 0.8 inches, in some places.

Further south and east, rain is expected to become much patchier. Large parts of England and Wales may receive only a few millimetres, while some southern locations could stay completely dry.

Wisley in Surrey has already gone well over a month without measurable rain, and it remains uncertain whether the area will record any rainfall on Friday or during the weekend.

Even where showers arrive, they are unlikely to make a meaningful difference to the wider water shortage caused by prolonged dry weather through spring and summer.

Which areas are facing water shortages?

A drought was officially declared on Thursday across large parts of north and mid-Wales. The remainder of Wales, along with much of central, southern and eastern England, is classified as being in “prolonged dry weather,” one level below drought status.

The Scottish Environment Protection Agency has also moved much of eastern Scotland into “water scarcity” status.

Meanwhile, hosepipe bans remain in force for millions of customers across eastern and southern England. The weekend rainfall forecast is not expected to bring much relief to areas already in drought or close to entering it.

The limited rain matters beyond the inconvenience of watering restrictions. Long dry periods can place pressure on farms, wildlife, rivers and public water supplies, while high temperatures increase health risks for people who are older, isolated or medically vulnerable.

Could another heatwave develop next week?

Forecast models suggest that the UK could see a strong north-south divide next week.

Weather fronts are expected to bring periods of rain to northern and western areas. Parts of Scotland, Northern Ireland and north-west England could receive their most significant rainfall in several weeks.

However, high pressure may strengthen over the south-east and cause those fronts to stall. If that happens, dry and increasingly hot weather could rebuild across much of England and Wales.

Temperatures may return to the low 30s in some places, creating the possibility of another period of heatwave conditions shortly after the weekend cooldown.

The longer-range outlook remains uncertain, particularly over exactly where the rain-bearing fronts will stop and how quickly high pressure may return. Local forecasts are therefore likely to change as the picture becomes clearer.