It's the BoM site, in Australia.
As a site its considerably less authorative than you seem to believe; people get weather warnings here in Australia from the TV, from the radio, from apps on their phones, from looking outside and seeing weather fronts rolling in.
Few people actually directly visit the BoM site, those that do are generally long time users familiar with the site using the usual array of adblockers and noscript, unlikely to fall for "Click here" injection attacks, and more likely to have a direct fibre | line connection to a major ISP to BoM with little chance for malicious injection in any case.
The risks are understood and doomsday scenarios have yet to occur after nearly 40 odd years online as a non https site.
