Nothing unseasonal about it, I reported the same pollution in
this thread. IMO all the pollution we're seeing is a direct result of year round forestry burnoff activity, I suspect the majority of it coming from the "ashtray isle" (Tas). The federal government are subsidising private forestry, from memory to the tune of $4600 per hectare. In Tasmania native forests are being decimated, and farmland is being converted to private forest at an unprecedented rate. We have a constant muddy coloured haze which clears only after heavy rains. There is not a day goes by that burnoffs are not happening and to top it off poison sprays (insecticides) are being used some of which have been banned for decades in other countries, then the growing forests are baited to keep out "grazing" animals. The end result is that the residues of these poisons are ending up in our waterways and the water tastes of burned ash after heavy rains. Add in the remains of whatever rotting dead animals happen to fall in catchment areas. If it's not happening in your area it probably soon will. If you produced this level of pollution from your backyard you would end up in court, but of course forestry is exempt from all environmental laws, at least here in Tas.
