And for the first time in almost 100 years, donkey rides were cancelled at a seaside resort in South Wales as it was too hot for the animals.
The heatwave also claimed its fourth victim after a 50-year-old man collapsed and died while hillwalking in the Lake District.
Polly Powell, 39, launched the campaign after her son, Jack Pullan, 13, was threatened with detention for taking 'smart shorts' to school in sweltering 86F heat.
More than 300 parents added their support to the petition after the incident on Monday, and Ysgol Dyffryn Aman school in Carmarthenshire agreed to change its policy.
The message they received read: 'Please be aware school will close on Wed 21 June at 11.30am due to increased heat.
Send your child in as normal and collect them at 11.30am.'A Hampshire County Council spokesperson said Andover Cof E is the only authority-run school in the area which planned to close today. At the end of the day they are trying to set an example to the children for real life.'Another parent called the decision 'a bit extreme'.
Barristers were granted an unusual dispensation to take off their horse hair wigs by judges in Croydon Crown Court.