I have an enormous tolerance for heat and warmth (my brother once joked that my presence was marked in one of his dreams by steam escaping from underneath the bathroom door - as happened in reality - for I like piping hot showers) and could not conceive of shorts and short sleeves in anything much under 18-20C.
43F clocks in at just over 6C......Brrrr. That is not just a pullover, but pullover, perhaps a jacket, and certainly some sort of an outer coat.
Yes, I imagine that it will get an awful lot colder in the winter. Here, it is 18C (64F) indoors, and 11C (52F) outdoors; both too cold - to my mind - for short sleeves, let alone shorts.
Stay warm, but, above all, enjoy yourself.