LONDON, June 20 -- British health officials are warning people across the country to take precautions when out in the sun as the UK. bakes under its first heat wave of the year.

Temperatures are expected to peak at 34 degrees Celsius (93 degrees Fahrenheit) in some parts of eastern England on Saturday following a week of unusually warm weather, according to the national weather agency the Met Office. That's about 12 C (22 F) higher than normal for this time of year.

The U.K. Health Security Agency has issued an amber heat health alert covering all of England because of increased health risks for people over 65 and those with heart and lung problems.

"Heat can result in serious health outcomes across the population, especially for older...