I'm always reading about people trying to keep tropical hoyas happy in colder climates but how do you keep the colder species cool in hot weather?

I have a few that are supposed to love growing in the colder parts of Australia. apparently . (bella, polyneura, serpens,) and from what I've seen they do love it! Serpens and polyneura have been growing and shooting out new growth everywhere and polyneura has grown a peduncle! Bella is full of buds and is looking like flowering really well.

Now we are having a bit of a heat wave and my cool loving hoyas are chucking tanties. Serpens has stopped growing shoots and is sulking and bella has blasted several smaller less developed peduncles. Who knows what polyneura thinks about it all?

Is there something I should be doing? Would misting them a bit help? It's easy to heat things up but how do you cool things down? Maybe they need to just tough it out?