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!!
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.
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.