Schools have been advised to stop pupils from playing football on sun-baked playing fields in case of accidents.
There are concerns over pitches as "hard as concrete" after the hot summer
Cambridgeshire County Council has warned schools that pupils might not realise that grass surfaces were "as hard as concrete" after the hot, dry summer.
The authority is concerned pupils could fall and hurt themselves.
Schools have been sent e-mails to bring the issue to teachers' attention.
"Schools in Cambridgeshire have been advised to think about restricting some sports on their playing fields as the ground could be unexpectedly hard following the record hot weather in the UK," a council spokesman said.
"Schools have been asked make a decision on their individual situation and local conditions.
"Children expect some surfaces to be hard, such as tarmac playgrounds, but may not understand the need for caution on a field."
The council's advice was endorsed by the Royal Society for the Prevention of Accidents (Rospa).
"It's the sensible thing to do to consider the potential dangers posed and avoid accidents and injuries where possible," a spokesman for the charity said.
"We don't want to go down the road of the nanny state and say 'Let's ban everything'. But this is quite a sensible thing to do - to warn schools that there could be a potential problem."
The charity urged teachers to carry out risk assessments of playing fields and recreation grounds.
"They will all have different types of facilities. Some ground may be suitable for a kick-about at football or a game of touch rugby but not for a full-scale game of rugby," the Rospa spokesman said.
"Some ground may have been rutted when it dried and be more dangerous because of that."