Shouldn't "Het waait." also be correct?
I like that. But I suppose it could be referring to a flag.
I've been told "het waait" is the accepted translation of "it is windy".
"Het is winderig" is colloquially used when somebody lets out a fart.
Do you never say simply "het is winderig"? I think you say "het is warm" and not necessarily "het is warm weer"?
It sounds perfectly acceptable to me, but perhaps use it judiciously considering LalitMahap's interpretation.