Temperature and UV are only part of it and probably a small part of it. Melbourne winters aren't even as cold as the UK, much less Scandanavia but winter drives oeople inside. Even here in Sydney, with temperatures far warmer than Melbourne, that would have people in the UK thinking about pub gardens and picnics, it is a cause to wrap up, wear beanies and stay inside. This is a big driver in Victorian infections.
Plus standards of what is acceptable here are different. 500 infections in a day and 5 deaths is enough for people to start considering stage 4 lockdowns and sending in the military to enforce it. NSW had 15 new infections, only 2 of which were untraced community infections and Qld are thinking of shutting the border.
Our government have recognised that eliminating community infection is the only real way to protect the economy until a vaccine. Which is bizarre given how incompetent they usually are.
And I have no proof that season is a huge factor but Europe seems to have benefited from summer just as Australia seems to have suffered for winter - pubs and restaurants that are now mainly inside with windows closed, to keep the heating in, would have outside seating full and if indoors windows and doors would be open in spring or summer. Only 6 more weeks of winter so I guess we will see.