The weather has been shifting for years. I remember 20 years ago some scientist suggested we needed to move the seasons as we know them to suit the weather.
Different parts of the country suffer vastly different humidity. Some areas are a very dry heat, some can be very humid. We had several days this summer where the humidity was so bad the tiles on the floor of the kitchen felt like they were sweating, but the temps weren't super high (95-100). Up north towards the tropics it's often humid and sticky, whereas over in CiGland it's more often a dry heat.
Bushfires are non discriminatory, they can burn happily in all weather. Dry conditions often create ideal places for lightning strikes to start fires, but incompetence and stupid can start them anywhere. Most of the large bushfires here create their own weather patterns so they really aren't fussy.