Such levels aren't usually reached until much later in the year. The deepest holes in the ozone appear every two years as a natural oscillation of air movements in the southern hemisphere brings heavy doses of ozone-destroying chemicals south. But the lows may not be due to this cycle. Very cold temperatures have been brought into the region by a vortex of very cold air which was offset this year towards South America. The BAS predicts that as temperature in the ozone layer drops further the situation will worsen.
Cold weather is bad news for ozone.