Cracking the flags?

[o9roberts]

every now and then i hear the expression "cracking the flags" or "it'll be cracking the flags today". This expression is normally made to describe an extremely hot day. But i was wondering if anyone knew where it originated and what it actually means.

I thought it might mean that'll be that hot it'll crack the paving flags?!??!?? But i'm probably wrong!!

[Quizmonster]

I'm pretty sure you are right about the flags being flag-stones rather than fluttery things on poles! If it referred to the latter, it would presumably mean that it was very windy rather than hot.

[heathfield]

The sun's rays are beating down on the flagstones with such intensity that they might crack from the heat, just as a rock can crack if it's put on an open fire.

[EllyD]

My Uncle always used to say "It is so hot, it is splitting the stones" - I always took it that he meant paving stones.