Don't know is it hotter today? for the first time in owning them the Meridian 557's both have dropped out on temperature, dammed inconvenient especially when shmbo is out and i've got the remote control.
It sure is warm out, reading 30 in my car driving back from yours.
I'm lucky enough to have air con so my kit is nice and chilled. Could be worth looking into as you could keep the windows closed and not get roasted even on a not so warm day. Your 557's probably heat the room a fair bit on their own.
I have a mixture of valves and class A in a rack with not much air space, so I run several 12v computer fans (at 5v to make them silent). These come on with the amps, so the extra heat recently hasn't caused any problems. Mind you, I'm stuck indoors convalescing so it's definitely affected me. It's made me spend £2300 on new hifi!
The Ming da MC7R has no apparent problems with heat neither has the Croft phono, as for the Atlas Magnum it sits in a corner shadowed by one of the OT Quad 57's so I have a pair of 12v computer fans in a metal frame running off a variable voltage wall wart set at 6v to slow & quiet fans they are 10" above the Atlas pulling air up so far no problems other than our well insulated flat is noticeably warm.