It is spring time in Sydney and this is the time when a lot of people in Sydney get hayfever. This is because spring is when a lot of plants have flowers and the pollen from the flowers is blown about by the wind. People with hayfever are allergic to some of these pollens and will react when they breath in the pollens. Asthma is another common disease. Asthma symptoms are caused by many things, including pollen, so some people with asthma may find spring a time of year when their asthma is worse the usual.
Some people get asthma when the air is polluted.
Sydney is a big city and a lot of people drive their cars to and from work each day. All these cars produce a lot of pollution in the air. Sydney's weather determines what happens to the air pollution that comes from Sydney's cars. In winter, when the air is very still, we tend to have a lot of another sort of air pollution. Today we have low air pollution, which is good.