What is a good alternative for a tie? Help required.

[Hal]

A tie with no jacket looks like the teenager going to his first job interview.

Thank you very much! That was how I looked on hot summer days (though never as hot as Americans often experience) throughout my long teaching career. I suspect this is a UK/USA cultural difference, as has been suggested earlier in this thread. With a long-sleeved shirt, (and also, in my opinion, flat-fronted and belted trousers) this look is entirely acceptable.

A jacket with no tie is saying, I want to dress but it's really hot here.

I still don't see why the jacket is worn in this case. To me, jacket with open-necked shirt simply looks incomplete. I've said this many times and don't suppose I'll "convert" any of you - but I loathe that look.